Methods and devices for soft tissue dissection

ABSTRACT

A differential dissecting instrument for differentially dissecting complex tissue is disclosed. The differential dissecting instrument comprises a handle and an elongate member having a first end and a second end, wherein the first end is connected to the handle. The differential dissecting instrument comprises a differential dissecting member configured to be rotatably attached to the second end and further comprises at least one tissue engaging surface. The differential dissecting instrument comprises a mechanism configured to mechanically rotate the differential dissecting member around an axis of rotation, thereby causing the at least one tissue engaging surface to move in at least one direction against the complex tissue. The at least one tissue engaging surface is configured to selectively engage the complex tissue such that the at least one tissue engaging surface disrupts at least one soft tissue in the complex tissue, but does not disrupt firm tissue in the complex tissue.

PRIORITY APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 61/687,587, entitled “Instrument for Soft TissueDissection,” filed on Apr. 28, 2012, which is incorporated herein byreference in its entirety.

The present application also claims priority to U.S. Provisional PatentApplication No. 61/744,936, entitled “Instrument for Soft TissueDissection,” filed on Oct. 6, 2012, which is incorporated herein byreference in its entirety.

The present application also claims priority to U.S. Provisional PatentApplication No. 61/783,834, entitled “Instruments, Devices, and RelatedMethods for Soft Tissue Dissection,” filed on Mar. 14, 2013, which isincorporated herein by reference in its entirety.

RELATED APPLICATIONS

The present application is related to U.S. Provisional PatentApplication No. 61/631,432, entitled “Methods and Devices To ReduceTissue Trauma During Surgery,” filed on Jan. 4, 2012, which isincorporated herein by reference in its entirety.

The present application is related to U.S. Provisional PatentApplication No. 61/632,048, entitled “Methods and Devices To ReduceTissue Trauma During Surgery,” filed on Jan. 17, 2012, which isincorporated herein by reference in its entirety.

BACKGROUND

Field of the Disclosure

The field of the disclosure relates to methods or devices used todissect tissue during surgery or other medical procedures.

Technical Background

Surgeons frequently are required to sever tissues during a surgicalprocedure. Two techniques are commonly used: (1) “sharp dissection” inwhich the surgeon uses a cutting instrument to slice a tissue, cuttingwith either scissors, a scalpel, electrosurgery, or other slicinginstrument and (2) blunt dissection.

Surgeons frequently are required to sever tissues during a surgicalprocedure. Two techniques are commonly used: (1) “sharp dissection” inwhich the surgeon uses a cutting instrument to slice a tissue, cuttingwith either scissors, a scalpel, electrosurgery, or other slicinginstrument and (2) blunt dissection.

The advantage of sharp dissection is that the cutting instrument easilycuts through any tissue. The cut itself is indiscriminate, slicingthrough any and all tissues to which the instrument is applied. This isalso the disadvantage of sharp dissection, especially when trying toisolate a first tissue without damaging it, when the first tissue isembedded in and obscured by a second tissue or, more commonly, in manytissues. Accidental cutting of a blood vessel, a nerve, or of the bowel,for example, is not an uncommon occurrence for even the most experiencedsurgeons and can lead to serious, even life-threatening, intra-operativecomplications and can have prolonged consequences for the patient.

Isolation of a first tissue that is embedded in other tissues is thusfrequently performed by blunt dissection. In blunt dissection, a bluntinstrument is used to force through a tissue, to force apart twotissues, or to otherwise separate tissues by tearing rather thancutting. Almost all surgeries require blunt dissection of tissues toexpose target structures, such as blood vessels to be ligated or nervebundles to be avoided. Examples in thoracic surgery include isolation ofblood vessels during hilar dissection for lobectomy and exposure oflymph nodes.

Blunt dissection includes a range of maneuvers, including various waysto tear soft tissues, such as the insertion of blunt probes orinstruments, inverted action (i.e., spreading) of forceps, and pullingof tissues with forceps or by rubbing with a “swab dissector” (e.g.surgical gauze held in a forceps). When needed, sharp dissection is usedjudiciously to cut tissues that resist tearing during blunt dissection.

The general goal is to tear or otherwise disrupt tissue, such asmembranes and mesenteries, away from the target structure withouttearing or disrupting either the target structure or critical structuressuch as nearby vessels or nerves. The surgeon capitalizes on thedifferent mechanical behaviors of tissues, such as the differentstiffness of adjacent tissues or the existence of planes of softertissue between firmer tissues. Frequently, the goal is to isolate atarget tissue that is mechanically firm, being composed of more tightlypacked fibrous components, and is embedded in a tissue that ismechanically soft, being composed of more loosely packed fibrouscomponents. More tightly packed fibrous tissues include tissues composedof tightly packed collagen and other fibrous connective tissues, usuallyhaving highly organized anisotropic distributions of fibrous components,often with hierarchical composition. Examples include blood vessels,nerve sheaths, muscles, fascia, bladders, and tendons. More looselypacked fibrous tissues have a much lower number of fibers per unitvolume or are composed of less well organized materials such as fat andmesenteries. Fibrous components include fibers, fibrils, filaments, andother filamentous components. When a tissue is referred to as “fibrous”,the reference is typically to extracellular filamentous components, suchas collagen and elastin—proteins that polymerize into linear structuresof varying and diverse complexity to form the extracellular matrix. Asmentioned in the previous paragraph, the density, orientation, andorganization of fibrous components greatly determine the tissue'smechanical behavior. Sometimes, tissues are referred to as “tough,fibrous tissues” indicating that the fibrous or filamentous componentsare densely packed and comprise a significant fraction of the bulk ofthe tissue. However, all tissues are fibrous, to one extent or another,with fibers and other filamentous extracellular components being presentin virtually tissue.

What is important to the present discussion is that softer tissues tearmore easily than firmer tissues, so blunt dissection attempts to proceedby exerting sufficient force to tear softer tissue but not firmertissue.

Blunt dissection can be difficult and is often time-consuming. Judgingthe force to tear a soft tissue, but not a closely apposed firm tissueis not easy. Thus, blood vessels can be torn. Nerves can be stretched ortorn. In response, surgeons attempt judicious sharp dissection, butblood vessels and nerves can be cut, especially a smaller side branch.This all leads to long, tedious dissections and increased risk ofcomplications, like bleeding, air leaks from the lungs, and nervedamage.

Surgeons frequently use forceps for blunt dissection. FIGS. 1A and 1Bshow a typical forceps 10 of the prior art. FIG. 1A shows the forceps 10in the closed position for clamping a tissue 34 between the opposingfirst clamp element 30 and second clamp element 31. FIG. 1B shows theforceps 10 in the open position, forcing tissue 34 apart. A first fingerengager 20 and an opposing second finger engager 21 are used to actuatethe mechanism. First finger engager 20 drives first clamp element 30,and second finger engager 21 drives second clamp element 31. A pivot 40attaches the first clamp element 30 and the second clamp element 31,permitting a scissor-like action to force the first clamp element 30 andthe second clamp element 31 together or apart, thereby clamping tissue34 between the two clamp surfaces 35 and 36 or rending tissue 34 by thespreading of the first clamp element 30 and the second clamp element 31.Frequently, a ratcheting clasp 50 is used to lock the first clampelement 30 and the second clamp element 31 together.

Laparoscopic and thoracoscopic (collectively referred here as“endoscopic”) instruments use a similar action. FIG. 2 shows an exampleof an endoscopic forceps 110 of the prior art. A first finger engager120 and an opposing second finger engager 121 are used to actuate themechanism. First finger engager 120 is rigidly mounted to the instrumentbody 150. Second finger engager 121 drives opposing clamp elements 130and 131. A pivot 140 attaches the two clamp elements 130 and 131, suchthat actuation of second finger engager 121 forces clamp elements 130and 131 together, thereby clamping a tissue between two clamp surfaces135 and 136. As in FIG. 1, endoscopic forceps 110 can be used to force atissue apart. Clamp elements 130 and 131 are closed, inserted into atissue, and then opened to tear the tissue.

For either instrument, forceps 10 or endoscopic forceps 110, a surgeonperforms blunt dissection by closing the forceps, pushing the closedforceps into a tissue and then, optionally, opening the forceps insidethe tissue, using the force applied by opening of the jaws of theforceps to tear the tissue apart. A surgeon thus proceeds to dissect atissue by a combination of pushing into the tissue and opening the jawsof the forceps.

Blunt dissection is commonly used for wet and slick tissues, and thesmooth, passive surfaces of most surgical instruments slide easily alongthe tissue, impairing the instrument's ability to gain purchase andseparate the tissue. Furthermore, the surgeon has only limited control,being able only to jab, move sideways, or separate. An improvedinstrument for blunt dissection that could differentially separate softtissues while not disrupting firm tissues would greatly facilitate manysurgeries.

SUMMARY OF THE DETAILED DESCRIPTION

Embodiments disclosed herein include methods and devices for bluntdissection, which differentially disrupt soft tissues while notdisrupting firm tissues. In particular, in one embodiment, adifferential dissecting instrument for differentially dissecting complextissue is disclosed. The differential dissecting instrument comprises ahandle and an elongate member having a first end and a second end,wherein the first end is connected to the handle. The differentialdissecting instrument also comprises a differential dissecting memberconfigured to be rotatably attached to the second end, the differentialdissecting member comprising at least one tissue engaging surface. Thedifferential dissecting instrument further comprises a mechanismconfigured to mechanically rotate the differential dissecting memberaround an axis of rotation, thereby causing the at least one tissueengaging surface to move in at least one direction against the complextissue. The at least one tissue engaging surface is configured toselectively engage the complex tissue such that when the differentialdissecting member is pressed into the complex tissue, the at least onetissue engaging surface moves across the complex tissue and the at leastone tissue engaging surface disrupts at least one soft tissue in thecomplex tissue, but does not disrupt firm tissue in the complex tissue.

In another embodiment, a differential dissecting member for dissecting acomplex tissue is disclosed. The differential dissecting membercomprises a body having a first end and a second end, with a centralaxis from the first end to the second end. The first end is configuredto be directed away from the complex tissue and configured to be engagedwith a drive mechanism that moves the differential dissecting membersuch that the second end sweeps along a direction of motion. The secondend comprises a tissue-facing surface that is configured to be directedtoward the complex tissue. The tissue-facing surface comprises at leastone tissue engaging surface comprised of an alternating series of atleast one valley and at least one projection arrayed along the directionof motion on the tissue-facing surface such that the intersection of theat least one valley and at least one projection define at least onevalley edge possessing a component of its direction perpendicular to thedirection of motion. In one embodiment, the at least one valley edge isnot sharp.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B show examples of the prior art. FIG. 1A shows forcepsused to grasp tissue;

FIG. 1B shows exemplary forceps used in blunt dissection to dividetissue;

FIG. 2 shows laparoscopic forceps of the prior art;

FIG. 3A through 3F show an exemplary differential dissecting instrument.FIGS. 3A through 3C show a differential dissecting instrument having arotating differential dissecting member within a shroud. FIG. 3D showsfront and side views of a differential dissecting member. FIG. 3E showsfour different types of differential dissecting members. FIG. 3F shows adifferential dissecting member in front and side view, including atissue to be dissected;

FIGS. 4A through 4F show how an exemplary differential dissectinginstrument disrupts soft tissue, but not firm tissue, in a complextissue, exposing the firm tissue. FIGS. 4D through 4F illustrate how adifferential dissecting member engages and disrupts tissues havingdispersed fibrous components but is unable to engage, and thus disrupt,fibrous components;

FIGS. 5A through 5C show the tissue engaging end of different exemplarydifferential dissecting instruments comprising a dissecting wheelmounted in a shroud. FIGS. 5A through 5B show an instrument with oneconfiguration of a dissecting wheel and FIG. 5C shows another instrumentwith a different configuration of a dissecting wheel;

FIGS. 6A through 6D show different configurations of an exemplarydifferential dissecting member in a differential dissecting instrumentshowing how the axis of rotation of the differential dissecting membercan have many different orientations with respect to the differentialdissecting instrument, including differential dissecting instrumentshaving flexible or articulating elongate members;

FIGS. 7A and 7B show an exemplary differential dissecting instrumentthat uses a dissecting wire instead of a dissecting wheel or otherdifferential dissecting member;

FIGS. 8A through 8C show an exemplary differential dissecting instrumentthat uses a flexible belt as a differential dissecting member;

FIGS. 9A through 9C show how a varying the exposure of the tissueengaging surface of a differential dissecting member changes thebehavior of a differential dissecting instrument, especially the rangeof angles of exposure of the tissue engaging surface;

FIGS. 10A through 10C show how a varying the exposure of the tissueengaging surface of a differential dissecting member changes thedirections of the friction forces on a tissue and thus the angles ofstrain on that tissue;

FIGS. 11A and 11B show an exemplary differential dissecting instrumentwith water outlets that emit beside the differential dissecting member;

FIG. 12 shows an exemplary differential dissecting instrument having twoopposing flexible belts that generate opposing frictional forces andthus reducing torque on the differential dissecting instrument;

FIG. 13 shows an exemplary differential dissecting instrument can havemultiple components placed into the shroud, including suction lines,water tubes, and light emitting diodes;

FIG. 14 shows how the elongate member of an exemplary differentialdissecting instrument can be articulated with a bendable region tofacilitate placement of the differential dissecting member;

FIGS. 15A through 15E show different exemplary differential dissectingmembers illustrating several important dimensions and features ofdifferential dissecting members;

FIG. 16 shows one exemplary means for changing the level ofaggressiveness of a differential dissecting member;

FIGS. 17A and 17B show how features, such as scalloping, of the tissueengaging surface result in the tissue engaging surface having varyingangles of attack as it moves over a tissue;

FIG. 18 shows how relative placements of the center of rotation and thecenter of gravity of an oscillating differential dissecting member cancause a differential dissecting instrument to vibrate;

FIGS. 19A through 19D show how an exemplary differential dissectingmember, or a shroud surrounding it, strain a tissue in the directionperpendicular to the direction of motion of the tissue engaging surface.FIG. 19D illustrates how this strain can align fibrous components insidethe tissue, thereby facilitating their disruption by the tissue engagingsurface;

FIG. 20 further illustrates how an exemplary differential dissectingmember disrupts tissue, including how the differential dissecting memberstrains the tissue and disrupts fibrous components, such as interstitialfibers;

FIGS. 21A through 21C shows how relative movement of the shroud and thedifferential dissecting member of a differential dissecting instrumentvary the wedge angle and thus can produce more or less strain in atissue;

FIG. 22 shows one example of an exemplary reciprocating mechanism for adifferential dissecting member that uses a scotch yoke mechanism toconvert rotation of a shaft to reciprocal oscillation of a differentialdissecting member;

FIGS. 23A through 23C further illustrate the scotch yoke mechanism shownin FIG. 22;

FIGS. 24A and 24B further illustrate the scotch yoke mechanism shown inFIG. 22;

FIGS. 25A through 24D further illustrate the scotch yoke mechanism shownin FIG. 22, including how more of the differential dissecting member canbe shrouded to reduce trauma to a patient's tissues;

FIGS. 26A and 26B show how an exemplary differential dissecting membercan be fitted with retractable blade to permit a differential dissectinginstrument to also perform sharp dissection of tissues;

FIGS. 27A and 27B show how an exemplary differential dissecting membercan be fitted with a clasping member to permit a differential dissectinginstrument to act as forceps;

FIG. 28 shows an exemplary differential dissecting member having atissue engaging surface and a lateral surface;

FIGS. 29A through 29E show magnified views of the tissue engagingsurface and lateral surfaces of the differential dissecting member inFIG. 28 with the tissue engaging surface being comprised of analternating series of valleys and projections;

FIG. 30 shows how the lateral surface of the differential dissectingmember in FIGS. 28 and 29A through 29C align and strain tissues,including interstitial fibrous components and how straining of theinterstitial fibrous components facilitates their alignment and enteringa valley and then being torn by a projection;

FIG. 31 further illustrates from a different view how fibrous componentsof a tissue enter a valley and are then strained and torn by aprojection;

FIG. 32 shows an exploded view of a complete exemplary differentialdissecting instrument;

FIGS. 33A through 33C show an enlarged view of the differentialdissecting member of the differential dissecting instrument in FIG. 32,with emphasis on how a scotch yoke mechanism permits a rotating shaft todrive the reciprocal oscillations of the differential dissecting member;

FIG. 34 shows an exploded view of another exemplary differentialdissecting instrument having a retractable blade;

FIGS. 35A through 35C show an enlarged view of the differentialdissecting member of the differential dissecting instrument in FIG. 34,including how this mechanism can also be used to vary the amplitude ofoscillation of the differential dissecting member;

FIGS. 36A and 36B show an exemplary retractable blade that is aretractable hook having a more aggressive tissue engaging surface plus ahook with a sharpened elbow permitting selective slicing of tissue forsharp dissection;

FIG. 37 illustrate how the retractable hook shown in FIGS. 36A and 36Bcan be used to quickly and safely divide a membranous structure, likethe peritoneum;

FIG. 38 shows a complete exemplary differential dissecting instrumenthaving a pistol grip and the ability to rotate the instrument insertiontube and, thus, turn the plane of oscillation of the differentialdissecting member;

FIG. 39 shows how an exemplary differential dissecting instrument can befitted to the arm of a surgical robot and can, optionally, be fittedwith an electrically conducting patch for electrocautery; and

FIG. 40 shows an exemplary laparoscopic version of a differentialdissecting instrument having electromechanical actuators distal to anarticulation.

DETAILED DESCRIPTION

Embodiments disclosed herein include methods and devices for bluntdissection, which differentially separate soft tissues while notdisrupting firm tissues. In particular, in one embodiment, adifferential dissecting instrument for differentially dissecting complextissue is disclosed. The differential dissecting instrument comprises ahandle and an elongate member having a first end and a second end,wherein the first end is connected to the handle. The differentialdissecting instrument also comprises a differential dissecting memberconfigured to be rotatably attached to the second end, the differentialdissecting member comprising at least one tissue engaging surface. Thedifferential dissecting instrument further comprises a mechanismconfigured to mechanically rotate the differential dissecting memberaround an axis of rotation, thereby causing the at least one tissueengaging surface to move in at least one direction against the complextissue. The at least one tissue engaging surface is configured toselectively engage the complex tissue such that when the differentialdissecting member is pressed into the complex tissue, the at least onetissue engaging surface moves across the complex tissue and the at leastone tissue engaging surface disrupts at least one soft tissue in thecomplex tissue, but does not disrupt firm tissue in the complex tissue.

In another embodiment, a differential dissecting member for dissecting acomplex tissue is disclosed. The differential dissecting membercomprises a body having a first end and a second end, with a centralaxis from the first end to the second end. The first end is configuredto be directed away from the complex tissue and configured to be engagedwith a drive mechanism that moves the differential dissecting membersuch that the second end sweeps along a direction of motion. The secondend comprises a tissue-facing surface that is configured to be directedtoward the complex tissue. The tissue-facing surface comprises at leastone tissue engaging surface comprised of an alternating series of atleast one valley and at least one projection arrayed along the directionof motion on the tissue-facing surface such that the intersection of theat least one valley and at least one projection define at least onevalley edge possessing a component of its direction perpendicular to thedirection of motion. In one embodiment, the at least one valley edge isnot sharp.

Specifically, “Differential Dissecting Instruments” are disclosed. Theterm “differential” is used because a Differential Dissecting Instrumentcan disrupt Soft Tissue while avoiding disruption of Firm Tissue. Theeffector end of a Differential Dissecting Instrument can be pressedagainst a tissue comprised of both Firm Tissue and Soft Tissue, and theSoft Tissue is disrupted far more readily than the Firm Tissue. Thus,when a Differential Dissecting Instrument is pressed into a ComplexTissue, the Differential Dissecting Instrument disrupts Soft Tissue,thereby exposing Firm Tissues. This differential action is automatic—afunction of the device's design. Far less attention is required of anoperator than traditional methods for blunt dissection, and risk ofaccidental damage to tissues is greatly reduced.

For the purposes of this application, “Soft Tissue” is defined as thevarious softer tissues separated, torn, removed, or otherwise typicallydisrupted during blunt dissection. “Target Tissue” is defined as thetissue to be isolated and its integrity preserved during bluntdissection, such as a blood vessel, gall bladder, urethra, or nervebundle. “Firm Tissue” is defined as tissue that is mechanicallystronger, usually including one or more layers of tightly packedcollagen or other extracellular fibrous matrices. Examples of FirmTissues include the walls of blood vessels, the sheaths of nerve fibers,fascia, tendons, ligaments, bladders, pericardium, and many others. A“Complex Tissue” is a tissue composed of both Soft Tissue and FirmTissue and can contain a Target Tissue.

FIGS. 3A, 3B, and 3C show the effector end of a Differential DissectingInstrument 300 that can differentially disrupt Soft Tissue while notdisrupting Firm Tissues. In this embodiment, a dissecting membercomprises a dissecting wheel 310 that rotates around shaft 320 that isheld inside cavity 331 inside shroud 330. FIG. 3A shows the separateparts. FIGS. 3B and 3C show two different views of the assembly. Thedissecting wheel 310 is turned by any of several mechanisms, such as amotor or a manually driven drive with appropriate means of transmission.Dissecting wheel 310 has tissue engaging surface 340 that can grab anddisrupt Soft Tissue but not Firm Tissue. Examples of tissue engagingsurface 340 and dissecting wheel 310 include a diamond grinding wheel oran abrasive stone or a surface otherwise covered by small obtrusions orprojections (further defined below) from the surface. Shroud 330obscures portions of dissecting wheel 310 such that only one portion ofdissecting wheel 310 is exposed. In use, dissecting wheel 310 rotates ata speed ranging from approximately sixty (60) to approximatelytwenty-five thousand (25,000) rpm or from approximately sixty (60) toapproximately one hundred thousand (100,000) rpm, with speed beingoperator selectable. Additionally, the direction of rotation ofdissecting wheel 310 can be reversed by the operator. Alternately,dissecting wheel 310 can oscillate (reciprocal oscillation) with afrequency ranging from about sixty 60 to approximately twenty thousand(20,000) cycles per minute in one embodiment. In another embodiment, thedissecting wheel 310 can oscillate (reciprocal oscillation) with afrequency ranging from about 2,000 to 1,000,000 cycles per minute.

Dissecting wheel 310 is one example of a “Differential DissectingMember” (hereinafter “DDM”) that can differentially disrupt Soft Tissuebut not Firm Tissue. FIG. 3D shows side, front, and oblique views of oneembodiment of a DDM 350 that has been separated from the rest of theDifferential Dissecting Instrument 300 for clarity. DDM 350 is comprisedof a body 360 having an axis of rotation 365 about which body 360rotates. Rotation can be oscillatory (i.e. back-and-forth) orcontinuous. Body 360 has an outer surface 361 with a tissue engagingsurface 370 distributed over at least a portion of the outer surface 361of body 360. Non-tissue engaging surface 371 is the portion of outersurface 361 not covered by tissue engaging surface 370. In thisembodiment, no portion of outer surface 361 that contacts a tissue, andespecially tissue engaging surface 370, should have features that aresufficiently sharp to slice tissue, so there should be no knife edges(like a scalpel or scissors), no sharply pointed teeth (like a saw), nosharp corners, and no sharp-edged fluting (like a drill bit or anarthroscopic shaver), where sharp means possessing a radius of curvatureless than 25 m. Typical maximum dimensions of a DDM are betweenapproximately three (3) and approximately twenty (20) millimeters (mm).Alternatively, a small version for microsurgery can measure betweenapproximately two (2) and approximately five (5) mm.

The tissue engaging surface 370 is further comprised of a plurality ofprojections 375 (shown in expanded detail view of FIG. 3D) from theouter surface 361 of body 360, each projection 375 having a projectionlength 380 measured from trough to peak in a direction substantiallyperpendicular to that local region of outer surface 361 of body 360.Different projections 375 on tissue engaging surface 370 can all havethe same projection length 380, or they can have different projectionlengths 380. Projections 375 preferably have a projection length 380less than approximately one (1) mm. Alternatively, for some embodimentsthe projection length can be greater than approximately one (1) mm butless than approximately five (5) mm. Collectively, all projections 375on a tissue engaging surface 370 have an average projection length(P_(avg)). Projections 375 are separated by gaps 385, preferablyspanning a distance of approximately 0.1 mm to approximately ten (10)mm.

Body 360 of FIG. 3D can optionally be shaped such that tissue engagingsurface 370 is located at varying distances from the axis of rotation365. Thus, a placement radius R can be measured in a plane perpendicularto the axis of rotation 365 from the axis of rotation 365 to any pointon tissue engaging surface 370. There will thus be a minimum placementradius R_(min) having the shortest length and a maximum placement radiusR_(max) having the longest length, and as shown in FIGS. 3D and 3E,R_(min) is greater than zero whenever the tissue engaging surface 370does not completely cover the surface 361 of the DDM 350. Thus, if body360 is shaped such that tissue engaging surface 370 is located atvarying distances from the axis of rotation 365, then (R_(max)−Rmin)will be greater than zero. In some embodiments of a DDM, thisrelationship (R_(max)−R_(min)) is greater than approximately one (1) mm.In other embodiments this relationship (R_(max)−R_(min)) is greater thanP_(avg). Alternatively, as shown in the examples in FIG. 3D and FIG. 3E,R_(min) is typically at least 5% shorter than R_(max). Typical sizes fora DDM are R_(min)>approximately one (1) mm and R_(max)<approximatelyfifty (50) mm; however, smaller versions for microscopic dissections canhave smaller dimensions of R_(min)>approximately 0.5 mm andR_(max)<approximately five (5) mm.

Referring now to FIG. 3E, four different embodiments of a DDM are shownin side view, with the axis of rotation 365 being perpendicular to theplane of the page. The cross-sectional profile of a DDM in a planeperpendicular to the axis of rotation 365 is important, as will bediscussed in subsequent paragraphs. Below are four scenarios for across-sectional profile of a DDM.

-   -   DDM Type I: The cross-sectional profile can be any shape, except        circular or a wedge of a circle. The axis of rotation 365 is        located at any point within the cross-section as shown in FIG.        3D that yields the result that P_(avg)<(R_(max)−R_(min)). As        shown in FIG. 3D, a DDM Type I can include regular        cross-sectional profiles and irregular cross-sectional profiles,        including various asymmetries, wavy/undulating/scalloped        borders, cut-outs, involute borders, etc. In this example, the        DDM Type I reciprocally oscillates between two end positions        (dotted outlines). Alternatively, motion can be rotational.    -   DDM Type II: The cross-sectional profile is circular or the        wedge of a circle. The axis of rotation 365 is located at any        point within the cross-section such that it yields the result        that P_(avg)<(R_(max)−R_(min)) (i.e. the axis of rotation 365 is        not close to the center of the circle).    -   DDM Type III: The cross-sectional shape is circular or the wedge        of a circle. The axis of rotation 365 is located at any point        within the cross-section sufficiently close to the center of the        circle such that it yields the result that        P_(avg)˜(R_(max)−R_(min)) (i.e. the axis of rotation 365 is        approximately at the center of the circle).    -   DDM Type IV: The cross-sectional shape has a regularly repeating        feature on the perimeter, such as scalloping, that yields the        result that P_(avg)<(R_(max)−R_(min)) no matter where the axis        of rotation 365 is located, including at the centroid of the        cross-sectional shape. A Type I DDM and a Type IV DDM are        closely related in that the axis of rotation 365 can be anywhere        within the cross-sectional shape and still yield the result that        P_(avg)<(R_(max)−R_(min)).

The scallops, undulations, or any regularly repeating feature of a DDMdo not include perforations or holes in the tissue engaging surface 370for which the walls of the perforations do not significantly contacttissue. For example, the aspirating passages disclosed in U.S. Pat. No.6,423,078 comprise holes in the abrasive surface, which act as thetissue engaging surface, of an abrading member. These holes do notcomprise the features disclosed for DDMs because the holes act only asfluidic ports in the tissue engaging surface, and the walls of theaspirating passages are not brought to bear on tissue. Nevertheless,DDMs disclosed herein can include aspirating passages such as these.

DDMs of Type I through IV can also include any variety of shape out ofthe plane of the page. As stated earlier, “The cross-sectional profileof a DDM in a plane perpendicular to the axis of rotation 365 isimportant”. Thus, dissecting wheel 310 in FIG. 3A through FIG. 3C is anexample of a DDM Type III.

FIG. 3F illustrates a DDM 390 that is similar to the DDM 350 shown inFIG. 3D. DDM 390 has a first end and a second end 392 wherein the firstend 391 is directed away from the Complex Tissue 399 and is rotatablyengaged with a mechanism (not shown) such that DDM 390 is rotated aboutan axis of rotation 365 by the mechanism. The mechanism can includemotorized and manual drives. The second end 392 is directed toward theComplex Tissue 399 and comprises a semi-ellipsoid shape defined by threeorthogonal semi-axes: the major semi-axis A, the first minor semi-axisB, and the second minor semi-axis C, wherein major semi-axis A lies inthe direction of a line connecting the first end 391 and the second end392; minor semi-axis C is parallel to the axis of rotation 365 (i.e. Ais perpendicular to the axis of rotation 365); and minor semi-axis B isperpendicular to both major semi-axis A and minor semi-axis C. Thesemi-ellipsoid can have a range of shapes (e.g., there may be differentrelationships between the lengths of the three semi-axes, includingA=B=C, A≠B≠C, A>B and A>C). In one embodiment, A>B>C to be veryeffective for a DDM.

FIGS. 4A through 4C show how the effector end of Differential DissectingInstrument 300 can be used for dissection of a Complex Tissue, whereinthe DDM is a dissecting wheel 310. In FIG. 4A, an operator initiatesrotation of dissecting wheel 310, as indicated by arrow 410, before orupon contact with a tissue mass 400. In FIG. 4B, the operator thenpresses the exposed tissue engaging surface 340 of dissecting wheel 310into the volume of the Complex Tissue 400 for blunt dissection to reachthe Target Tissue 420 within. The arrows 430 and 440 in FIG. 4B show twopossible operator-executed motions of the Differential DissectingInstrument 300. Only the portion of tissue engaging surface 340 ofdissecting wheel 310 exposed outside of shroud 330 contacts the tissue400 and thereby disrupts that portion of tissue 400 in contact withtissue engaging surface 340. Because the exposed, moving portion oftissue engaging surface 340 can disrupt tissue without further action bythe surgeon (e.g. without the surgeon's forcefully scrubbing aDifferential Dissecting Instrument 300 against tissue 400), tissue canbe disrupted simply by application of the rotating dissecting surface340 of dissecting wheel 310 to any part of tissue 400; however, whendissecting wheel 310 contacts the Firm Tissue of Target Tissue 420, itdoes not disrupt the Target Tissue 420. Note that pushing dissectingwheel 310 into tissue 400 as indicated by the arrowhead on arrow 430 isa “plunge”—the dissecting wheel 310 can be pushed blindly into tissue400 because it will not disrupt Firm Tissue and will, therefore, notdisrupt Target Tissue 420. Other motions of Differential DissectingInstrument 300 can be used to dissect tissue 400, including motionorthogonal to arrows 430 and 440, curvaceous motions, and other 3Dmotions. Once Target Tissue 420 has been exposed, DifferentialDissecting Instrument 300 can be withdrawn, exposing the Target Tissue420, as shown in FIG. 4C.

FIG. 4D through FIG. 4F show how one embodiment of a DDM disrupts SoftTissue but won't disrupt Firm Tissue. FIG. 4D depicts a sectional viewof a DDM as dissecting wheel 310 with tissue engaging surface 340 havingprojections 375. Dissecting wheel 310 moves in and out of the plane ofthe page, with shaft 320 (not shown) substantially parallel to the planeof the page. The projections 375 thus move through the plane of thepage. FIG. 4D further shows a volume of Soft Tissue 400 that remainssubstantially in place as dissecting wheel 310, tissue engaging surface340, and projections 375 travel through the plane of the page. Given themotion of the projections 375 relative to the roughly stationary SoftTissue 400, dissecting wheel 310 disrupts Soft Tissue 400. In detail,the Soft Tissue 400 is comprised of both fibrous components 401 andgel-like material 402. (Soft Tissues are frequently composed ofextracellular material with fibrous components 401, e.g. collagen fibersand small bundles of fibers, and with thin sheet components, e.g.thinner membranes, dispersed in water-swollen gel-like materials.)Projections 375 are capable of sweeping through gel-like material 402such that they encounter and then snag individual fibrous components 401(e.g. at points 450 and 451); fibrous components 401 are then torn bythe relative motion of projections 375 on the dissecting wheel 310through the plane of the page and Soft Tissue 400. As dissecting wheel310 is pushed deeper into tissue 400, projections 375 will snag deeperand deeper fibrous components, also tearing them. Thus, Soft Tissues 400with dispersed components can be dissected with a DDM.

FIG. 4E shows, in contrast to FIG. 4D, how a tightly packed fibroustissue can resist dissection by a dissecting wheel 310. Firm Tissues 403are frequently comprised of fibrous components 401 that are tightlypacked either into parallel, crossed, or other organized arrays (e.g.fascia and blood vessel walls), or into tightly packed 2D and 3D meshes,and a gel-like material 402 covers the arrays of fibrous components 401.In FIG. 4E, a Firm Tissue 403 is composed of a gel-like material 402(stippled region) thinly coating a layer of tightly packed fibrouscomponents 401, the filaments of which are depicted with their long axesperpendicular to the plane of the page, thus the cross-section of thefibrous components 401 is depicted as circular. In this image thedissecting wheel 310 reciprocally oscillates left-right on the page, asindicated by arrow 405, sweeping projections 375 over the surface ofFirm Tissue 403. Due to the tight packing of fibrous components 401 inthis Firm Tissue 403, projections 375 are unable to separately engageand snag fibrous components 401, and are thus unable to apply sufficientstress to tear fibrous components 401. Furthermore, gel-like material402 serves as a lubricant, causing projections 375 to tend to slip offof the tightly packed fibrous components 401 of Firm Tissue 403.Finally, any compliance of the surface of Firm Tissue 403 exposed todissecting wheel 310 will prevent developing tension in the Firm Tissue403 or fibrous components 401, resulting in the Firm Tissue 403deflecting away from any pressure exerted by dissecting wheel 310. FirmTissues 403 thus resist disruption by DDMs by a combination of tightpacking of fibrous and sheet components 401, lubrication of thesecomponents by gel-like materials 402, and compliance of the Firm Tissue403.

Motion of a DDM, as stated above, can be either rotational oroscillatory. The velocity of a point on a DDM past a specific region oftissue strongly influences the ability of a DDM to disrupt that tissue.FIG. 4F depicts a dissecting wheel 310 that sweeps left-right within theplane of the page (as shown by double headed arrow 460) over a SoftTissue 400 with a point of contact 470. The translational velocity ofpoint of contact 470 is determined by the rotational velocity of the DDMand the distance 480 separating point of contact 470 from the center ofrotation (not shown). For rotational motion, the translational velocityequals 2πDω, where D is the distance 480 and ω is the rotationalfrequency in rotations per second. For oscillatory motion, thetranslational velocity equals DΨ2X, where D is the distance 480, Ψ isthe oscillatory frequency in cycles per second, and X is the angle sweptin radians. For a differential dissector, distance 480 ranges from aboutone (1) mm to about forty (40) mm; rotational velocity ranges fromapproximately two (2) rotations per second to approximately threehundred fifty (350 rotations per second; oscillatory frequency rangesfrom about two (2) hertz (Hz) to about three hundred fifty (350) Hz; andangle swept ranges from 2° to 270°. Thus, the translational velocity ofpoint of contact 470 on a differential dissector can range from aboutone (1) mm per second to about sixty thousand (60,000) mm per second. Inone embodiment, a distance 480 of approximately fifteen (15) mm and anoscillatory motion with frequency of approximately one hundred (100) Hzsweeping through about forty-five degrees (45°), yielding abouttwenty-four hundred (2400) mm per second, is very effective for a numberof Soft Tissues. Note that this means that the velocities ofoperator-executed motions (as shown in FIG. 4) are always smaller thanthe velocity of a point of contact on a DDM during dissection becausesurgeons are careful during dissections, moving their instruments onlyslowly (usually much less than one hundred (100) mm per second).Additionally, motion of the DDM is described throughout this document asarising from a rotational motion (continuous rotation or reciprocal,i.e., back-and-forth, oscillation). However, any motion of a DDM,including rectilinear motion, relative to a tissue such that the tissueengaging surface of the DDM appropriately engages the tissue, asdescribed above, can be used.

A DDM can be forced against a blood vessel wall, the pleura, thepericardium, the esophagus, the gall bladder, and almost any other organor tissue comprised of or covered by a tightly packed fibrous tissue,and the DDM will not significantly disrupt such a Firm Tissue underlight hand pressure. Conversely, a DDM can be forced against a mesenteryor other Soft Tissue, and the Soft Tissue will rapidly disrupt underlight hand pressure. Differential dissectors fitted with any one of avariety of DDMs as disclosed herein have been found by the inventors torapidly dissect between the planes of lobes in the lung, to dissect aninterior mammary artery away from the inner wall of the chest, toseparate the blood vessels and bronchiole in the hilum of a lung lobe,to dissect the esophagus from surrounding tissues, to penetrate throughbulk muscle between, rather than through, the fiber bundles, to dissectfascia and tendons away from muscle fibers, to clean dissected fascia,to expose branched vascular and lymphatic structures, to dissect pocketsinto tissues and to separate tissue planes in many different tissues.The utility of a differential dissector is broad has many potentialuses. Importantly, due to the composition of skin and of surgicalgloves, the skin or surgical gloves are not cut or otherwise disruptedby a DDM, even when significant pressure is applied. Thus, adifferential dissector is inherently safe to use, which simplifies useduring surgery, especially when the surgeon's fingers must be near thepoint of dissection.

DDMs are preferably formed from a rigid material, such as a metal or arigid polymer (e.g., Shore A equal to or greater than 70), rather thanfrom softer polymers and elastomers (e.g. Shore A less than 70). Use ofa rigid material keeps the projections from the tissue engaging surfacefrom deflecting away from the tissue, as might occur if a softermaterial was used. DDMs or their component portions can be machined frombulk material, constructed via stereolithography, molded by any of themeans well known in the art (e.g. injection molding), or by any suchmethod known in the art.

The projections of a tissue engaging surface of a DDM can be fabricatedby any of several means. Projections can be formed by coating the tissueengaging surface with grit similar to sandpaper using grit coarser than1000 but finer than 10 on the Coated Abrasive Manufacturers Institutestandard. Grit can include particles composed of diamond, carborundum,metal, glass, sand or other materials known in the art. Projections canbe formed into the surface of the material composing a DDM by sanding,sandblasting, machining, chemical treatment, electrical dischargemachining, or other methods known in the art. Projections can be moldeddirectly into the surface of a DDM. Projections can be formed onto thesurface by stereolithography. Projections can be irregularly shaped,like particles of grit, or they can be regularly shaped having definedfaceted, curved, or sloped surfaces. The projections may be elongate,and the long axis of these projections may have an angle with respect tothe tissue engaging surface. Projections possess a cross-sectional shapewhen viewing the tissue engaging surface from above, and this shape maybe round, faceted, or complex. The cross-sectional shapes of projectionsmay be oriented with respect to the direction of travel of the DDM.

Keeping the tissue wet helps differential dissection. A well-wetted FirmTissue is better lubricated, greatly reducing disruption by a DDM.Conversely, a well-wetted Soft Tissue remains water-swollen and soft,separating the spacing of individual fibers, facilitating their beingengaged and torn by the projections from the tissue engaging surface ofa DDM. Wetting of the tissue can be accomplished by any of severalmeans, including simply irrigating the tissue with physiological salineduring dissection. Irrigation can be performed with procedures alreadyused in surgery, such as an irrigation line, or by one of the devicesdisclosed below. Additionally, wetting of the tissue, and thus also thetissue engaging surface of the DDM, reduces clogging of the tissueengaging surface with disrupted tissue.

FIG. 5A and FIG. 5B show another embodiment of the effector end of aDifferential Dissecting Instrument 500 which has a DDM Type IIIconfigured as a circular cylinder 510. FIG. 5A shows circular cylinder510, with shaft 520 separate from the shroud 530. The tissue engagingsurface 540 covers the side of circular cylinder 510. The two-headedarrow indicates rotation about the axis of rotation 575. FIG. 5B showsboth parts configured for use with only a limited portion of tissueengaging surface 540 exposed.

FIG. 5C shows another embodiment of the effector end of a DifferentialDissecting Instrument with a different configuration for the shroud andDDM, here another DDM Type III. FIG. 5C shows a Differential DissectingInstrument 550 with a dissecting wheel 560, with shaft 570 separate fromthe shroud 580. Tissue engaging surface 590 covers the periphery ofdissecting wheel 560. The two-headed arrow indicates the axis ofrotation 575. FIG. 5D shows both parts configured for use with only alimited portion of tissue engaging surface 590 exposed. Thisconfiguration is problematic because shroud 580 makes it difficult toposition the tissue engaging surface 590 against a tissue, and shroud580 blocks the operator's view.

FIG. 6A shows one embodiment of a Differential Dissecting Instrument 600that includes a handle 610 for an operator. Handle 610 connects toelongate member 620 comprising a first end 621 connected to handle 610and a second end 622 connected to a DDM 630. Elongate member 620 can beshorter, allowing better manual control of the DDM 630 on an instrumentfor open surgery, or it can be longer, allowing Differential DissectingInstrument 600 to be a laparoscopic instrument. The drive mechanisms forrotating DDM 630, such as a rotating drive shaft for a Scotch yoke or acrank/slider, are readily adapted to any elongate member 620, long orshort, or to any device capable of driving DDM 630. DDM 630 is a TypeIII DDM rotatably mounted to elongate member 620 at second end 622 suchthat DDM 630 reciprocally oscillates about its axis of rotation 640, asindicated by the double-headed arrow (Axis of rotation 640 isperpendicular to the plane of the page in FIG. 6A). First end 621 andsecond end 622 define a centerline 650 of elongate member 620. Thetangent 651 of centerline 650, as centerline 650 approaches second point622, and axis of rotation 640 thus define a presentation angle 670 (notshown—perpendicular to page). In this example, the presentation angle670 is 90° (i.e., axis of rotation 640 is aligned perpendicular totangent 651). Rather than a handle 610, first end 621 of elongate member620 can attach to the arm of a robot for robotic surgery. A DDM caneasily be adapted to any other device capable of moving or rotating theDDM.

FIG. 6B shows another embodiment of a similar Differential DissectingInstrument 601 but with the axis of rotation parallel to the centerline.Handle 610 connects to elongate member 620 comprising a first end 621connected to the handle 610 and a second end 622 connected to a Type IIIDDM 631. DDM 631 is rotatably mounted to elongate member 620 at secondend 622 such that DDM 631 reciprocally oscillates about its axis ofrotation 640. The axis of rotation 640 is parallel to the plane of thepage in FIG. 6B. First end 621 and second end 622 define a centerline650 of elongate member 620 with tangent 651 as centerline 650 approachessecond end 622. Axis of rotation 640 is thus aligned parallel to tangent651 (i.e., the presentation angle 670 is 0°). (Again, presentation angle670 is not presented in FIG. 6B because presentation angle is 0°.)Differential Dissecting Instrument 601 is thus similar to DifferentialDissecting Instrument 550 in FIG. 5C and thus has similar limitations,including that it is difficult to position the tissue engaging surfaceof DDM 631 against a tissue without blocking the operator's view.

FIG. 6C shows another embodiment of a Differential Dissecting Instrument603 having a curved elongate member 620 with curved centerline 650 andtangent 651 to centerline 650 as centerline 650 approaches second point622. The axis of rotation 640 is perpendicular to tangent 651 formingpresentation angle 670, which is 90° in this example. Elongate member620 may similarly be bent, jointed, articulated, or otherwise made of aplurality of parts. In all cases, the presentation angle 670 is formedby the axis of rotation of a DDM and the tangent of the centerline as itapproaches second point 622.

FIG. 6D shows another embodiment of a Differential Dissecting Instrument604 similar to Differential Dissecting Instrument 602 in FIG. 6B. Handle610 connects to elongate member 620 comprising a first end 621 connectedto the handle 610 and a second end 622 connected to a Type III DDM 631.DDM 631 is rotatably mounted to elongate member 620 at second end 622such that DDM 631 reciprocally oscillates about its axis of rotation640. The axis of rotation 640 is parallel to the plane of the page in.6B. First end 621 and second end 622 define a centerline 650 of elongatemember 620 with tangent 651 as centerline 650 approaches second point622. Axis of rotation 640 is thus aligned at a non-zero angle to tangent651 (i.e., the presentation angle 670 is between 0° and 90°). Inpreferred embodiments, presentation angle 670 does not equal 0°, for thereasons described for Differential Dissecting Instrument 603 in FIG. 5Cand FIG. 6B.

FIG. 7A and FIG. 7B show another embodiment of the effector end of aDifferential Dissecting Instrument 700 that uses a dissecting wire 710as the DDM. FIG. 7A shows the assembled device. Dissecting wire 710stands out a distance 725 from the backing surface 726 of a shroud 730,the dissecting wire 710 emitting from a first post 720, spanning gap722, and entering a second post 721 on the end of shroud 730. Dissectingwire 710 is a continuous loop of wire driven such that the exposedsection of dissecting wire 710 travels in the direction indicated byarrow 723 across gap 722 in FIG. 7A.

FIG. 7B shows a schematic side view of this embodiment of a DifferentialDissecting Instrument 700 that depicts the loop of dissecting wire 710and drive mechanism. Dissecting wire 710 is a continuous loop thatpasses over a first idler bearing 750 housed in first post 720 and thenemits from first post 720. Dissecting wire 710 travels across gap 722,moving in the direction of arrow 723, and enters second post 721 whereit passes over second idler bearing 751. The loop of dissecting wire 710travels further back in shroud 730 where it passes over a drive wheel760 which is turned by, for example, a motor in the direction of curvedarrow 724. Thus, rotation of drive wheel 760 drives dissecting wire 710.Note that dissecting wire 710 can be a flexible linear element with anycross-sectional shape, so instead of being a wire of circularcross-sectional shape, dissecting wire 710 could be a flexible flat beltwith the outward-facing side possessing a tissue engaging surface.Similarly, dissecting wire 710 can be a flexible cord having greaterdiameter than a wire would permit turning over idler bearings 750 and751; the flexible cord having a tissue engaging surface. Further, thedistance 725 between the dissecting wire 710 and the backing surface 726can be arbitrarily large or small, for example the distance 725 can belarge enough to create a substantial area encircled by the dissectingwire 710, the backing surface 726 and the first post 720 and the secondpost 721, thus able to surround a Target Tissue to be removed. Incontrast, distance 725 can be zero, where the dissecting wire 710 runsalong the surface of the shroud 730, or even in a slight accommodatinggroove that supports the dissecting wire 710 from behind. Such anaccommodating groove can have a semi-circular cross-sectional shape thusexposing just a portion of the cross-sectional shape of the dissectingwire 710 to the tissue to be dissected. Further, the shape of thebacking surface 726 can be flat, or it can be curved, subtly orpronounced, and the curved surface can possess convex areas, concaveareas, or a combination.

FIG. 8A-8C show the effector end of a Differential Dissecting Instrument800 that uses a flexible belt as the DDM. FIG. 8A shows the separateparts. Flexible belt 840 has an outer tissue engaging surface 850.Flexible belt 840 travels over idler wheel 810, which rotates aroundshaft 820, all of which are housed in shroud 830.

FIG. 8B shows the assembled effector end of Differential DissectingInstrument 800 with only a limited portion of tissue engaging surface850 of flexible belt 840 exposed.

FIG. 8C shows a top view of a schematic of one example of how a flexiblebelt, such as flexible belt 840, can be driven. Idler wheel 810 anddrive wheel 860 are mounted inside shroud 830. Flexible belt 840 wrapsaround idler wheel 810 and drive wheel 860. Drive wheel 860 is poweredto rotate such that flexible belt 840 is driven in the directionindicated by curved arrow 870. The tissue engaging surface 850 exposedoutside the shroud 830 is then used to disrupt tissue. The drive wheel860 can be driven by any of several mechanisms, such as a motor, handcrank, etc. The drive wheel 860 and the idler wheel 810 need not beright circular cylinders, nor must their rotational axes be parallel.

The extent of exposure of tissue engaging surfaces outside of theshrouding can be greater or less than those shown in the prior examples.In fact, varying the exposure changes several aspects of the behavior ofthe Differential Dissecting Instruments.

First, a larger exposure, increases the exposed area of the tissueengaging surface, which increases the amount of tissue disrupted perunit time and increases the surface area of tissue removed. Thus,decreasing the exposure allows more precise removal of tissue, but itreduces the total amount of material removed. Second, increasing theexposure changes the angle of exposed tissue engaging surface. ConsiderFIGS. 9A through 9C, which show top view schematics of the effector endof Differential Dissecting Instrument 800 with successively restrictedexposure of tissue engaging surface 850 as controlled by the aperture900 in the shroud. Aperture 900 is largest in FIG. 9A and smallest inFIG. 9C. As the exposure is restricted, the range of angles of thearrows normal to tissue engaging surface 850 decreases. In FIG. 9A, thetissue engaging surface 850 disrupts both forward and on the sides. InFIG. 9C, the tissue engaging surface 850 disrupts only forward. Thus,when the tissue engaging surface 850 is applied to a tissue, differentdirections of contact are applied, depending on the angle of the exposedtissue engaging surface.

Second, this increasing angle of exposure of the tissue engaging surface850 also changes both the angles at which the contacted surface of atissue is strained and the torque on the instrument. Consider FIGS.10A-10C which show the friction on a tissue 400 created by applicationof a tissue engaging surface 1010.

In FIG. 10A, tissue engaging surface 1010 is moving in the direction ofarrow 1020. This produces a friction force in the direction of arrow1030. The larger the area of contact, the larger the friction force. Thefriction force both pulls the tissue 400 sideways (in the direction ofarrow 1030), shearing the tissue 400, and forces the tissue engagingsurface 1010 in the direction opposite arrow 1020. If tissue engagingsurface 1010 is mounted on an instrument 1060 at a distance from thepoint 1040 held by an operator, then the friction force places a torque1050 about point 1040. This torque can cause the end 1070 opposite point1040 of instrument 1060 to be pulled away from the desired point ofapplication, making control of dissection more difficult. Thus, limitingthe extent of exposure of a tissue engaging surface reduces the frictionforce and improves control by reducing torque on the handle.

FIG. 10B shows how a circular tissue engaging surface 850 producesfriction forces normal to the tissue engaging surface 850 and thus, indifferent directions depending on the range of contact of the tissue 400on the circular tissue engaging surface 850. The resultingmultidirectional shearing forces on the tissue 400 produce more complexstrain patterns in the tissue 400. As in FIG. 10A, the friction forcestill produces a net upward force 1080 on the tip of shroud 830;however, it does not produce a net left/right (into and out of thetissue 400) force on the tip of shroud 830. FIG. 10C shows that reducingthe exposure of tissue engaging surface 850 by narrowing aperture 900makes the friction force on the tissue more 1-dimensional, simplifyingstrain patterns in the tissue.

Despite this discussion of friction against a tissue, as discussed abovewith respect to wetted tissues, a DDM as described herein has theunusual quality of being effective when it has low friction with respectto a Complex Tissue. The non-tissue engaging surface and the tissueengaging surface are effective even when the entire DDM is fully bathedwith a lubricant, such as a surgical lubricant or a hydrogel lubricant.

In surgery, it is preferable to minimize unintended transport of tissuesto other parts of the body. Disrupted pieces of tissue can adhere to thetissue engaging surfaces of the Differential Dissecting Instrumentsdisclosed here. Unintended transport can be minimized in two ways.First, narrowing and controlling the shape of the aperture 900 as shownin FIG. 10B and FIG. 10C means that fragments of disrupted tissueadhering to the tissue engaging surface 850 will only be transported ashort distance before being deposited on or entering the shroud.Similarly, if they attach to but are then thrown tangentially away fromthe tissue engaging surface 850 by inertia, then narrowing the aperture900 will reduce the surface area available for adhesion, the timeavailable for adhesion and the distance that material can beaccelerated. Second, the tissue engaging surface 850 can be maderesistant to tissue adhesion. Surface treatment of a tissue engagingsurface 850 can be achieved by any of several techniques known in theart, such as chemical treatment, vapor deposition, sputtering, andothers. For example, fluorinating the tissue engaging surface 850 by anyof several known methods (e.g. dip coating, chemical deposition,chemical cross-linking such as with silanes, etc.), can make the tissueengaging surface 850 resist tissue adhesion by both hydrophilicmaterials and carbon-based hydrophobic tissue components. In oneembodiment, diamond/carbide coated tissue engaging surfaces may be used,which we have discovered to be much less likely to have tissue adhere tothese surfaces.

Transport of materials can also be reduced by the use of an oscillating(reciprocating) motion of the DDM, rather than a continuousunidirectional or continuous rotational motion. Oscillation preventstransport over distances exceeding the distance of oscillation, whichcan be over only a few degrees of rotation (e.g. 5 degrees to 90degrees). Any of a number of mechanisms can be used to drivereciprocating oscillating motion with a rotating motor, such as a Scotchyoke or crank/slider.

Tissue adherence is also a problem for decreasing the effectiveness ofthe tissue engaging surface 850. Clogging of the tissue engaging surface850 creates a thick coat of material over the tissue engaging surface850, making it much less effective at ablating Soft Tissue. As above,making the surface resistant to adhesion by tissues decreases thisproblem. Fluorinated tissue engaging surfaces and diamond/carbide tissueengaging surfaces don't clog as readily, especially when disruptingfatty tissues.

Clogging is also reduced if the tissue is wet and further if the tissueengaging surface 850 is flushed with water, as discussed earlier. FIG.11A and FIG. 11B show a Differential Dissecting Instrument 1100 in whicha first array of 3 water outlets 1111 emits beside tissue engagingsurface 850 from shroud 830. A second array of 3 water outlets 1112emits on the opposite side of tissue engaging surface 850. Otherarrangements of water outlets are possible. FIG. 11A shows a solid modelin oblique view. FIG. 11B shows the top view for a schematic ofDifferential Dissecting Instrument 1100 in which water tube 1121 carrieswater, or other fluid such as physiological saline, inside and to oneside of shroud 830 to water outlets 1111, and a second water tube 1122carries fluid inside and to the other side of shroud 830 to wateroutlets 1112. Water outlets 1111 and 1112 emit from opposite sides ofaperture 900, providing fluid to both sides of tissue engaging surface850. The liquid emitting from water outlets can, optionally, carryphysiologically active materials, either dissolved or suspended in theliquid. Physiologically active materials can include variouspharmaceutical compounds (antibiotics, anti-inflammatories, etc.) andactive biomolecules (e.g. cytokines, collagenases, etc.)

Appropriate arrangement of tissue engaging surfaces 850 creates frictionforces on tissues that can be used to advantage during blunt dissection.FIG. 12 shows a Differential Dissecting Instrument 1200 having two,opposing flexible belts 1201 and 1202 exposed in aperture 1230. Eachbelt is configured as in FIG. 10B with flexible belt 1201 running overidle 1211 and flexible belt 1202 running over idle 1212, but theflexible belts 1201 and 1202 circulate in opposite sense with respect toeach other. Thus, the flexible belt 1201 and the flexible belt 1202 runside by side in the same direction as shown by arrows 1203 and 1204 butin opposite directions when exposed to the tissue 1205, as shown byarrows 1271 and 1272. Thus, the flexible belt 1201 creates a net force1251 downward and the flexible belt 1202 creates a net force 1252 upwardon shroud 1220, whereby these forces 1251 and 1252 cancel, leavinglittle or no net force on the shroud 1220. This eliminates any torqueingof Differential Dissecting Instrument 1200 (as described in FIG. 10A),making it easier for an operator to control. Additionally, the opposingdirections of motion 1271 and 1272 of flexible belts 1201 and 1202create opposing frictional forces on tissue 1205 during dissection,thereby pulling the tissue 1205 apart in the region identified by doubleheaded arrow 1260. This pulling action can facilitate blunt dissectionby tearing the tissue in the region of double headed arrow 1260. Notethat the gap 1280 between flexible belts 1201 and 1202 inside shroud1220 can be varied and can be reduced to zero such that flexible belts1201 and 1202 are in contact. Contact between flexible belts 1201 and1202 can help a drive mechanism match the rates of travel of flexiblebelts 1201 and 1202. In fact, friction between flexible belts 1201 and1202 can allow one belt, for example 1201, to drive the other belt, inthis example 1202. Thus a motor, for example, can actively driveflexible belt 1201, and flexible belt 1202 is then driven by flexiblebelt 1201. This can simplify the drive mechanism for two belts.

FIG. 13 shows how the shroud 1330 of a Differential DissectingInstrument 1300 can house other items, permitting greater functionality.Dissecting wheel 810 is exposed at aperture 900. Suction lines 1301 and1302 can connect to the front of the shroud 1330 near tissue engagingsurface 850, helping to remove any debris from disruption or excessfluid, such as fluid from water tubes 1121 and 1122 which emit throughwater outlets 1111 and 1112. Light emitting diodes (LEDs) can be placedon shroud 1330 to better illuminate an area for blunt dissection; forexample, LEDs 1311 and 1312 are supplied with power by cables 1313 and1314, respectively, and light from LEDs 1311 and 1312 directlyilluminates the tissue in the region of disruption.

FIG. 14 shows how the elongate member 1410 of a Differential DissectingInstrument 1400 can be articulated with a bendable region 1430 such thata user can achieve variable bending of the elongate member 1410 tofacilitate placement of the DDM 1420. In Position 1, the elongate member1410 is straight. In Position 2 and then in Position 3, elongate member1410 is successively bent at bendable region 1430 such that the DDM 1420moves from forward-facing in Position 1 to side-facing in Position 3.Bendable region 1430 can be an articulated joint or any other mechanismto permit bending.

FIGS. 15A-15E show different DDMs, illustrating several importantdimensions and features of DDMs. FIG. 15A shows a top view of a DDM 1500that rotates about a rotational joint 1510. Actuation of DDM 1500 causesit to reciprocally oscillate up and down, as shown by the double headedarrow 1506 such that tissue engaging surface 1520 (pebbled section)swings through an arc with radius R_(A). Oscillation of DDM 1500 canswing through a range of ±90 degrees. The tissue engaging surface has aminimum radius R_(S) in the plane of rotation (the plane perpendicularto the plane of rotation—the plane of the page here).

FIG. 15B shows a side view in cross-section with two successivelyenlarged views. (DDM 1500 thus oscillates in and out of the page in thisview.) First side 1530 and tissue engaging surface 1520 join at firstmargin 1540, having a radius of curvature R_(E), and second side 1531and tissue engaging surface 1520 join at second margin 1541, havingradius of curvature R_(E), where the radii of curvature of first margin1540 and second margin 1541 can be different, but should be large enoughsuch that the first margin 1540 and the second margin 1541 are notsharp. Tissue engaging surface 1520 is then created by projections 1550with a maximum length L_(max), defined as the maximum length of afeature from the innermost trough to the outermost peak.

FIG. 15C illustrates a different DDM 1501 having a scalloped tissueengaging surface formed by surface features 1560. Here, the surfacefeature 1560 is a convex lobe, but a surface feature 1560 can be anyregular or repeating feature on the tissue engaging surface 1520 havinga minimum radius of curvature R_(S). Furthermore, surface features canhave a profile that is not in the plane of rotation, as shown in FIG.15D and FIG. 15E. FIG. 15D shows an oblique view and FIG. 15E shows anend-on view. The inserts in FIG. 15E show successively magnifiedsections of the DDM 1502 taken along the 45° angle. DDM 1502 has surfacefeatures 1570 with a profile in a plane at 45° to the plane of rotation.As with DDM 1501 in FIG. 15C, the tissue engaging surface 1520 of DDM1502 has projections 1550 with a maximum length L_(max). In oneembodiment, R_(A) can be between approximately one (1) mm andapproximately one hundred (100) mm. In one embodiment, R_(S) can bebetween approximately 0.1 mm and approximately ten (10) mm. In oneembodiment, R_(E) can be between approximately 0.05 mm and approximatelyten (10) mm, such that no slicing edge is presented to a tissue.Alternatively, for some embodiments of a DDM, Rs and Re can be as smallas about 0.025 mm.

DDMs can have tissue engaging surfaces that are scalloped, or notched,or have undulating profiles such that the angle of attack of the tissueengaging surface with respect to the surface of the tissue varies as thetissue engaging surface passes over a given point in the tissue. Infact, the angle of attack varies for any DDM for whichP_(avg)<(R_(max)−R_(min)), e.g. for a DDM Type I, Type II, or Type IV. Avarying angle of attack makes the dissecting action more aggressive, inwhich a more aggressive DDM is better able to disrupt a firmer tissueand a less aggressive DDM is less able to disrupt that same tissue.

FIG. 16 shows an alternate means by which DDMs can be made withdifferent levels of aggressiveness, i.e. the aggressiveness of a DDM canbe designed. DDM 1600 rotates about an axis of rotation 1610 and has atissue engaging surface 1620 bearing projections 1620. These projectionshave more pointed tips (but still not sharp enough to slice). DDM 1640has a tissue engaging surface 1650 bearing projections having morerounded tips 1652. DDM 1680 has a tissue engaging surface 1690 bearingprojections with even more rounded tips 1692. DDM 1600 is moreaggressive than DDM 1640 which is more aggressive than DDM 1680.

FIG. 17A shows one embodiment of a DDM 1700 having a scalloped tissueengaging surface 1710 and a center of rotation 1720. DDM 1700 is thus anexample of a DDM Type IV. Oscillation of DDM 1700 back and forth asshown by double headed arrow 1730 causes tissue engaging surface 1710 tomove over a tissue such that the edges of the scallop bring the tissueengaging surface 1710 to bear at different angles of attack as eachscallop passes over the tissue.

FIG. 17B illustrates the action of DDM 1700 against a tissue 1750. Theangle of attack (the angle θ between the direction of motion and thetangent to the tissue engaging surface 1710 at a point of contact) isshown at two points P₁ and P₂ on the tissue engaging surface 1710. θ₁ issmaller than θ₂. Similar action can be achieved with a DDM 1800, asshown in FIG. 18, by using a circular tissue engaging component 1805with tissue engaging surface 1810 and a center of rotation 1820 that isnot the center of circular tissue engaging component 1805 (e.g., a DDMType II). Oscillation of tissue engaging component 1805 back and forthas shown by double headed arrow 1830 causes tissue engaging surface 1810to move over a tissue such that the tissue engaging surface 1810 movessuch that the angle of attack varies at each point on the tissueengaging surface 1810 on the perimeter of the circular tissue engagingcomponent 1805.

FIG. 18 illustrates another important point, especially for acceleratingmotions of a DDM against a tissue 1850, and accelerations occur whenevera DDM is loaded or unloaded and whenever an oscillating DDM deceleratesafter sweeping one direction and accelerates to sweep in the oppositedirection. DDM 1800 is mounted with its center of gravity 1870 displacedfrom the center of rotation 1820. The solid double-headed arrow 1830shows the rotation about the center of rotation 1820, and the dasheddouble-headed arrow 1840 shows the motion of center of gravity 1870. Theforce of accelerating the mass of DDM 1800 and the distance between thecenter of gravity 1870 and the center of rotation 1820 create a momentabout the center of rotation 1820 which causes a differential dissectorto vibrate. This moment will cause the handle of a differentialdissector, to which the DDM 1800 is attached, to shake. DDMs composed ofdenser materials will make the shaking more extreme. It can, thus, beadvantageous to make DDMs from less dense materials, like rigid polymersrather than metals, to decrease shaking of the handle. Conversely, onemight arrange a countering moment through appropriate distribution ofmass within a DDM to place the center of gravity at the axis ofrotation.

The entirety of the surface of a DDM can be tissue engaging.Alternatively, selected portions of the surface can be tissue engaging.This can be advantageous to restrict dissection effects to one region ofthe surface of the DDM, the forward-looking surface, for example. FIG.19A through FIG. 19D show a Differential Dissecting Instrument 1900 thathas a DDM that is a dissecting wheel 1910 that is similar to that shownin FIG. 3A through FIG. 3C; however, the tissue engaging surface isrestricted to a thin tissue engaging strip 1920 around the outerperimeter of dissecting wheel 1910 which rotates around axis of rotation365. The remainder comprises the non-tissue engaging surface 1930,disposed laterally to either side of tissue engaging strip 1920, of theexposed surface of the dissecting wheel 1910 and has a much smoothersurface, optionally being glass smooth, free of projections, orotherwise unable to engage fibers in the tissues. FIG. 19B illustrateshow a dissecting wheel 1910 fits into shroud 1940 and is pressed by anoperator in the direction 367. As FIG. 19C illustrates, non-tissueengaging surface 1930, which is smoother than tissue engaging strip1920, reduces disruption of tissue 1950 after it has been separated bytissue engaging strip 1920. Shroud 1940 further protects tissue 1950from disruption by dissecting wheel 1910 as the dissector penetratesfurther into tissue 1950 in the direction of pressing 367.

FIG. 19D illustrates an additional, important action of non-tissueengaging surface 1930 and of shroud 1940. When there is a component ofmotion 1901 in the direction of pressing 367 (not shown here) ofDifferential Dissecting Instrument 1900 into tissue 1950, these widerportions (non-tissue engaging surface 1930 and of shroud 1940) ofDifferential Dissecting Instrument 1900 force apart, or wedge, recentlyseparated portions of tissue 1950, aligning and straining the fibrouscomponents 1980 of tissue 1950, putting them in tension and aligningthem perpendicular to the motion of tissue engaging strip 1920. Thisstrain in fibrous components 1980 facilitates the ability of theprojections of the tissue engaging materials in tissue engaging strip1920 to grab and tear individual fibers.

As tissue engaging strip 1920 moves past tissue 1950, moving in adirection perpendicular to (and so through) the plane of the page, theprojections on tissue engaging strip 1920 therein disrupt tissue 1950,including tearing individual fibrous components 1980 of tissue 1950(e.g. collagen or elastin fibers). Such fibrous components 1980frequently have irregular alignments (i.e., irregular orientations) inSoft Tissues. However, as tissue 1950 is disrupted, DifferentialDissecting Instrument 1900 pushes into tissue 1950 in the direction ofcomponent of motion 1901 such that as remaining tissue engaging surface1930 and shroud 1940 push into the separated tissue 1950, they pushtissue 1950, including severed fibrous components 1990, aside in thedirection of arrows 1960 and 1961, aligning previously irregularlyoriented fibers and straining material at the point of contact of tissueengaging strip 1920. This local region of strain aligns and strains (andso pre-stresses) unsevered fibrous components 1980 in a directionperpendicular to the direction of motion of tissue engaging strip 1920,as shown by double-ended arrow 1970, facilitating their being grabbedand increasing the likelihood of their being severed by projections fromtissue engaging strip 1920. Non-tissue engaging surface 1930 and ofshroud 1940 will act as a wedge if they are angled with respect to oneanother, as shown in FIG. 19C and FIG. 19D or even if they have a widththat is wider than the tissue engaging surface 1910. In one embodiment,a semi-ellipsoid shape, as described in FIG. 3F, in which the secondminor semi-axis C is a significant fraction of the first minor semi-axisB (e.g., in one embodiment, where 0.2B<C<0.8B), is an effective shapefor wedging.

Alignment of fibers, as described in the preceding paragraph, cangreatly alter how a DDM performs. Alignment can be achieved by thesurgeon straining a tissue in the appropriate directions with theirhands or with a separate instrument. Alignment can be achieved by theDDM, as described in the preceding paragraph, by a smooth portion on atissue engaging wheel, such as non-tissue engaging surface 1930 in FIG.19C through FIG. 19D, by a smooth shroud, such as shroud 1940 in FIG.19A through FIG. 19D, or by a separate mechanism on a DDM.

FIG. 20 shows details of one version of disruption of tissue segments ina human patient. The region of interest 2000 of the patient is depictedwithin a circular window, showing a section view through two apposedvolumes, namely a tissue segment A apposed to a tissue segment B; theapposition occurs in a region 2010 bridged by both interstitial fibers2012 and taut interstitial fibers 2015 and further associated withbroken interstitial fibers 2020. Also depicted in the circular window isa DDM 2030 possessing a tissue engaging surface 2034 that furtherpossesses projections 2032 and a smooth non-tissue engaging surface2033. In this view, the DDM 2030 reciprocates about an axis 2036, sothat the motion of the fiber-engaging projections 2032 is in and out ofthe plane of the page (i.e., reciprocally toward and away from theviewer).

Each of the tissue segment A and tissue segment B further has a tissuesegment surface 2005 and a tissue segment surface 2006, respectively,composed of relatively tightly packed fibers aligned parallel to tissuesegment surface 2005 and tissue segment surface 2006, forming amembranous covering over tissue segment A and tissue segment B (e.g.,tissue segments A and B comprise Firm Tissues). Tissue segment A'ssurface 2005 and tissue segment B's surface 2006 are alsothree-dimensionally curvaceous. While these tissue segment surfaces 2005and 2006 may not be in contact with one another at every point, tissuesurface 2005 and tissue segment surface 2006 do meet in a region 2010where tissue segment surface 2005 and tissue segment surface 2006 areapposed in a locally, roughly parallel manner, and are frequentlysubstantially in contact with one another.

In that region 2010, the tissue segment surface 2005 and the tissuesegment surface 2006 are secured to one another by a population ofrelatively loose interstitial fibers 2012 that run substantiallyperpendicularly to the two apposed tissue segment surfaces 2005 and2006. This sparse population of interstitial fibers 2012 may or may notalso be derived from (or be members of) the populations of fiberscomprising the more tightly packed woven surfaces the tissue segmentsurfaces 2005 and 2006. For example, a given fiber comprising part of atissue segment surface 2005 may run along that surface for some distancebefore turning away and continuing across the region 2010, therebybecoming a member of the population of interstitial fibers 2012, andfurther, may continue across the region 2010 to tissue segment surface2006, where it can turn and interweave therein, thereby becoming amember of the population of fibers comprising tissue segment surface2006. Thus, the definition of interstitial fibers 2012 includes anyfibers crossing, bridging, traversing or otherwise connecting (orintimately associated with) the region 2010 where tissue segment surface2005 and tissue segment surface 2006 are in apposition. The interstitialfibers 2012 may be the same type of fibers as those comprising thetissue segment surface 2005 and tissue segment surface 2006 of tissuesegment A and tissue segment B in one embodiment. In another embodiment,the interstitial fibers 2012 may be a distinct type, and theinterstitial fibers 2012 may be strongly or weakly bound, directly orindirectly, to the tissue segment surface 2005 and the tissue segmentsurface 2006.

In each case, all fibers involved are mechanically capable oftransmitting force (via tension) either along the surface of eachindividual tissue segment, or interstitially, between the two tissuesegments, or both. For example, the state of tension of the interstitialfibers 2010 and the fibers comprising the tissue segment surface 2005and the tissue segment surface 2006 depends on the forces that act upontissue segment A and tissue segment B, for example when smoothnon-tissue engaging surface 2033 wedges into and forces apart thesetissue segments in the directions 1960 and 1961. For example, the fibers2010 resist tensile strains that arise from the motion of tissue segmentsurface 2005 in the direction 1960 and the motion of tissue segmentsurface 2006 in the direction 1961 relative to one another, and further,this resistance varies according to the mechanical properties of thefibers. For example, if the unstrained interstitial fibers 2012 arealigned perpendicularly to the two apposed tissue segment surfaces 2005and 2006, then the distance between tissue segment A and tissue segmentB may be increased (as shown by arrow 2030) until the interstitialfibers 2010 first become straightened like the taut interstitial fibers2015, and then finally the fibers may fail, as is shown by the brokeninterstitial fibers 2020. The most common fiber type in humans iscollagen, which possesses a breaking strain of about 5% beyondunstressed normal length. If tissue segment A and tissue segment B aremoved apart as shown by arrow 2030, the collagen fibers (here,unstrained interstitial fibers 2012) will first become taut (as are tautfibers 2015). If the two tissue segments A and B are moved even furtherapart, collagen fibers will stretch about 5%. Crucially, at this point,if tissue segment A is moved further than 5% beyond taut from tissuesegment B, either the taut interstitial fibers 2015 will break, or, ifthe taut fibers 2012 do not break, the tissue segments themselves mayrupture, with deleterious consequences for the patient.

Since surgeons very often must separate, dissever, or otherwise movetissue segments with respect to one another to gain access to variousareas inside patients, surgeons are constantly straining fiberpopulations equivalent to interstitial fibers 2010 throughout patients'bodies. Current practice requires either slicing interstitial fibers tofree one tissue segment from another, or tearing interstitial fiberswholesale by applying blunt force with forceps (by opening the jaws,forcing the tissue segments apart, and so tearing the interstitialfibers). Common complications are either slicing into the tissuesegments while attempting to cut only the interstitial fibers via sharpdissection, or, tearing off smaller or larger portions of the tissuesegments while attempting blunt dissection of the interstitial fibers.Either approach first strains to tautness the interstitial fibers 2010,then stretches them, and then tears them. The consequences (for example,air leaks and bleeding of segments of the lung) of the aforementionedintimate connection of the interstitial fibers 2010 with the tissuesegment surfaces 2005 and 2006 now becomes clear: one must segregate theforces required to cause the interstitial fibers to fail without alsosubjecting the integrated tissue segments themselves to the same forces.

The embodiments of the Differential Dissecting Instruments disclosedherein are specifically designed to segregate forces on fiberpopulations by generating an initial separating motion of apposed tissuesegments A and B via impingement of the smooth surfaces 2033, thusexposing and tensioning (pre-stressing) individual interstitial fibers2010, making these fibers much more likely to break, exploiting theopportunity provided by these now taut interstitial fibers 2015, andfurther allowing those to be discreetly encountered, engaged andconverted into broken interstitial fibers 2020 by the local impingementof projections 2032 of the tissue engaging surface 2034 of theDifferential Dissecting Member 2030. In this way, a DDM having asmooth-sided non-tissue engaging surface and/or shroud can greatlyincrease both the speed and effectiveness of dissection of tissues whilelimiting the extent of that dissection effect to just those fiberswithin Soft Tissues that connect adjacent regions of Firm Tissues andstill preserving those Firm Tissues.

FIG. 21A through FIG. 21C illustrate another Differential DissectingInstrument 2100 that uses a very thin dissecting wheel 2110 as the DDM.Dissecting wheel 2110 is nearly entirely wrapped in a shroud 2120 toachieve a very thin tissue engaging surface 2009 with shroud 2120 actingto protect, separate and pre-stress the tissue to be dissected, as shownin FIG. 19D.

FIG. 21A shows a side view, and FIG. 21B shows a front view. Dissectingwheel 2110 is mounted on two posts, first post 2130 and second post 2131(seen in side view of FIG. 21B), via rotational axle 2135. Rotationalaxle 2135 is free to rotate within first post 2130 and second post 2131,but is firmly affixed to dissecting wheel 2110. Sprocket 2140 is alsofirmly affixed to axle 2135. Sprocket 2140 is turned by drive belt 2150.Thus, a drive mechanism 2160 is created by first post 2130 and secondpost 2131, axle 2135, sprocket 2140, and drive belt 2150 to turndissecting wheel 2110 inside shroud 2120 in the direction of arrow 2161.Alternate drive mechanisms can be used, and motion can either berotational or oscillatory. The first margin 2111 and second margin 2112of dissecting wheel 2110 preferably are not sharp, as shown in theenlarged portion of FIG. 21B. (First and second margins 2111 and 2112are like first and second margins 1540 and 1541 in FIG. 15B.) Sharpmargins can disrupt more aggressively than a rounded margin;nevertheless, a sharper margin can be used if more aggressive disruptionor even disrupting is desired. Furthermore, one margin can be sharperthan the other if a differential disruption or disrupting is desired.For example, first margin 2111 can be square or even sharp, while secondmargin 2112 can be rounded to achieve more aggressive disruption ordisrupting on the side of first margin 2111.

Shroud 2120 nearly encloses dissecting wheel 2110, leaving only a fineportion of dissecting wheel 2110 exposed as the tissue engaging surface2111, and forming a wedge angle w that determines the strain on tissueat the point of disruption of dissecting wheel 2110. Larger wedge anglesw strain tissue more as DDM 2100 is pushed into a tissue. FIG. 21Cdepicts DDM 2100 with shroud 2120 in four different positions. Shroud2120 can be moved independently of drive mechanism 2160 and dissectingwheel 2110, shroud 2120 being able to move in the direction of doubleheaded arrow 2190. Thus, in Position 1 only a thin portion of dissectingwheel 2110 is exposed. In Position 2, shroud 2120 has been moved in thedirection of arrow 2191, leaving a thinner portion of dissecting wheel2110 exposed and also creating a larger wedge angle ω. In Position 3,shroud 2120 has been moved in the direction of arrow 2192 such thatshroud 2120 completely encloses dissecting wheel 2110. Thus, dissectingwheel 2110 can no longer disrupt tissue. In this position, thedissecting wheel 2110 effectively acts as a smooth, flat, blunt probe.In Position 4, shroud 2120 has moved in the direction of arrow 2193,increasing the exposure seen in Position 1 or Position 2 of dissectingwheel 2110 and decreasing wedge angle ω.

FIG. 22 shows the distal end of a differential dissector 2210, includingone embodiment of a reciprocating mechanism, here a scotch yoke. Thedistal end of differential dissector 2210 includes a housing 2212, whichfurther contains a pivot bearing 2214, a motor shaft bearing 2216, and ashaft drum bearing 2218. FIG. 22 also shows a motor shaft 2220, a shaftdrum 2222 coaxial with and affixed to the motor shaft 2220, and a driverpin 2224 which may be parallel but not coaxial to motor shaft 2220, andis itself affixed to the shaft drum 2222. Further, there is aDifferential Dissecting Member, DDM 2230, which is associated with thedifferential dissector housing 2212, and further comprises an outersurface 2231 defining the body of the DDM 2230, a tissue engagingsurface 2232 forming at least a portion of the outer surface 2231, a DDMpivot shaft 2234 that fits into the pivot bearing 2214, and furthercomprises a hollow DDM pin follower 2236 that effectively captures thedriver pin 2224. The internal three-dimensional shape of the hollow DDMpin follower 2236 is here shown as a prism, so that in the view shown inFIG. 22 the cross-sectional shape resembles an hourglass, whileperpendicular to that view, the cross-sectional shape is rectilinear.

FIG. 23A, FIG. 23B, and FIG. 23C show a sectional view a portion of theDDM 2230 of FIG. 22 through the narrowest portion of the waist of thehourglass-shaped hollow DDM pin follower 2236 and perpendicular to therotational axis of the shaft drum 2222. The shape of the DDM pinfollower 2236 is in this view rectangular; further, in this view showingthe dimensions through the waist of 2236 the height of the rectangle isequal or larger than a diameter described by the outer diameter of thedriver pin 2224 along its circular path 2237. The width of the rectanglein this view corresponds to the outer diameter of the driver pin 2224.The DDM 2230 containing the hollow DDM pin follower 2236 rotates aboutthe axis 2233 of the shaft 2234. Thus, the position of the hollow DDMpin follower 2236 and so the rotational position of the DDM 2230 isdetermined by the rotational position of the driver pin 2224.

In operation, referring to FIG. 22, along with FIGS. 23A-23C, the motor(not shown) turns the motor shaft 2220, which turns the drum 2222 aboutits axis of rotation, which causes the driver pin 2224 to travel about acircular path 2237, the plane of which is here perpendicular to therotational axis of the drum 2222. As in a scotch yoke, the rectangularlyhollow DDM pin follower 2236 converts the rotational path 2237 of thedriver pin 2224 into linear travel 2238 of the hollow DDM pin follower2236; given that the pin follower 2236 is located some distance awayfrom the axis 2233, the DDM 2230 is leveraged about the axis 2233, soconverting the rotational path 2237 into linear travel 2238 and soreciprocating motion of the DDM 2230 rotating about the DDM pivot shaft2234 held by the pivot bearing 2214. The pattern of the reciprocalmotion of the DDM 2230 can be controlled by varying the shape of thehollow DDM pin follower 2236, the driver pin 2224, the 3D angle of theaxis 2233 about which the shaft 2234 rotates, the distance from thedriver pin 2224 to the axis 2233, and also by varying the rotationalspeed of the motor.

The DDM 2230 of FIG. 22 may have reciprocating motion 2250 and 2251, asshown in side view in FIG. 24A and FIG. 24B. The oscillation sequenceshown depicts the extreme positions of the DDM 2230 as the driver pin2224 travels about circular path 2237 when provided with rotationalmotion 2299 from the motor (not shown). The action of the tissueengaging surface 2232 of the DDM 2230 on the surface of the tissues tobe dissected is best shown in edge-on view in FIG. 20.

A surgeon operating inside a patient desires to create the least traumapossible to tissues which are not the focus of the procedure, or aresimply in the way of the Target Tissue. To this end, FIGS. 25A through25C depict the profile view of an embodiment of a largely shrouded DDMassembly 2500, further comprising a shrouded pivot shaft 2510 thatprojects perpendicularly to the page (i.e., at the viewer), an internalmotor shaft 2550, an internal driver drum 2522, a driver pin 2524, a DDIhousing 2512, a DDM 2520 that reciprocates about the shrouded pivotshaft 2510 (and so within the plane of the page), a tissue engaging DDMsurface 2534, a smooth DDM surface 2518, a substantially circular DDMregion 2516, a shroud margin 2517, and a shroud-DDM gap 2514. Consideredas a whole, with all exterior surfaces of the DDM assembly 2500 includedas one, a shrouded DDM assembly 2500 presents a nearly continuous smoothsurface to a patient's tissues. In this regard, other than the limitedextent of the tissue engaging DDM surface 2534, the entire DifferentialDissecting Instrument fitted with the DDM assembly 2500 acts likenothing more than a polished probe.

Once activated, the DDM 2520 reciprocates within and relative to thehousing 2512. At the edge of the housing 2512 closest to the DDM 2520 isthe shroud margin 2517. Between the shroud margin 2517 and the DDM 2520is found the shroud-DDM gap 2514. In one embodiment, a DifferentialDissecting Instrument fitted with a DDM assembly 2500 includesprovisions for preserving the outwardly smooth character of theDifferential Dissecting Instrument. The shroud-DDM gap 2514 thuspresents a challenge, in that any relative motion of the DDM 2520 withrespect to the housing 2512 could enlarge the shroud-DDM gap 2514,presenting sharp edges to the tissues. Alternatively, a portion of theDDM 2520 could impact the housing 2512. Also, in one embodiment, theshroud-DDM gap 2514 is kept as small as possible at all times. Tofacilitate this, the DDM 2520 has a circular DDM region 2516, defined inthis perspective as a portion of the mass of the DDM 2520 having thecross-section of a circle with its center coincident with the axis ofthe shrouded pivot shaft 2510. This circular DDM region 2516 defines andoccupies that portion of the outer surface of the DDM 2520 that passesthe shroud margin 2517 during reciprocating motion of the DDM 2520, andat a distance that defines the shroud-DDM gap 2514. Because the circularDDM region 2516 preserves over the angle of rotation the same radius ofDDM 2520, this preserves the shroud-DDM gap 2514 at a constant value(i.e., shroud-DDM gap 2514 does not change despite motion of the DDM2520). Thus, the Differential Dissecting Instrument that is fitted withthis DDM assembly presents to the tissues a continuously smooth surfaceeverywhere through time.

FIG. 25D depicts an oblique view of the largely shrouded DDM assembly2500, showing a housing 2512, a DDM 2520 that reciprocates about theshrouded pivot shaft 2510 (see FIGS. 25A through 25C), a tissue engagingDDM surface 2534, a smooth DDM surface 2518, a substantially circularDDM region 2516, a shroud margin 2517, and a shroud-DDM gap 2514.

Sharp dissection is frequently performed alternately with bluntdissection when exposing a Target Tissue. This occurs whenever amembrane or a large fibrous component, which resists blunt dissection,is encountered and must be severed for the surgeon to penetrate furtherinto a tissue. Current practice requires that a surgeon either use asuboptimal instrument for blunt dissection (e.g., an inactiveelectrosurgery scalpel) or to swap instruments while exposing a TargetTissue. Use of a suboptimal instrument decreases the ease of bluntdissection and increases potential risk to a Target Tissue. Swappingconsumes time and is distracting, especially for many minimally invasiveprocedures in which the instrument must pass through a narrow orifice inthe body wall and then be gently guided to the site, such as duringlaparoscopy and thoracoscopy. A Differential Dissecting Instrument canbe equipped with a sharp dissecting component that can be selectivelyactivated by a surgeon, eliminating the need for instrument swappingwhile still providing the surgeon with an optimal instrument.

FIG. 26A shows a top and side view of one embodiment of a DifferentialDissecting Instrument 2600, similar to Differential DissectingInstrument 2000, as shown in FIG. 20, but now also comprising aretractable scalpel blade that is covered during blunt dissection. Theretractable scalpel blade can be projected outward by a surgeon forsharp dissection and then retracted before proceeding with further bluntdissection. Differential Dissecting Instrument 2600 has an elongatemember comprised of shroud 2620 to which DDM 2610 is rotatably mountedvia rotational axle 2635. To one side of DDM 2610 is a slot 2612 underwhich lies retractable scalpel blade 2622 such that retractable scalpelblade 2622 is completely covered by shroud 2620. Retractable scalpelblade 2622 is actuated by a retraction mechanism (not illustrated)controlled by a surgeon. Actuation of the retractable scalpel blade 2622can be controlled manually via a slider, by electrical actuation (suchas a solenoid), or by any suitable mechanism controllable by anoperator.

FIG. 26B shows Differential Dissecting Instrument 2600 with retractablescalpel blade 2622 extended for sharp dissection. Retractable scalpelblade 2622 is one example of a sharp dissecting tool. In otherembodiments, the Differential Dissecting Instrument 2600 could includeother sharp dissection tools, such as an electrosurgery blade,ultrasonic cutter, or a disrupting hook. In other embodiments, theDifferential Dissecting Instrument 2600 could include a tool forenergetic disruption, for example an electrocautery blade orelectrosurgery head. Additionally, instead of retraction, retractablescalpel blade 2622, or other suitable tool, could be selectively beexposed for use by one of several mechanisms, such as by pop-out, byunfolding, or other mechanism known in the art.

FIG. 27A and FIG. 27B show another embodiment of a DifferentialDissecting Instrument 2700, similar to Differential DissectingInstrument 2600 shown in FIG. 26A and FIG. 26B, but now possessing agrasping member 2750 to allow the Differential Dissecting Instrument2700 to also function as forceps. FIG. 27A shows the DifferentialDissecting Member (DDM) 2710 active, with a forceps functionality in aclosed position. FIG. 27B shows the DDM 2710 in an inactive state, withthe forceps functionality in an open position. Differential DissectingInstrument 2700 has a DDM 2710 rotatably attached to an instrument shaft2720 and is rotated by a motorized mechanism (not shown). A push rod2730 is inside instrument shaft 2720 and is activated by a mechanismresiding in a handle (not shown) and activated manually by an operator.When DDM 2710 is active, it oscillates back-and-forth as indicated byarrow 2740 (as shown in FIG. 27A). When the operator switches off theaction of DDM 2710, the operator can then push with push rod 2730 onforceps jaw 2750 which has a control horn 2760 that causes forceps jaw2750 (also known as a “clasping member”) to rotate around pivot point2770 and thus to open (as shown in FIG. 27B). The opposing jaw for theforceps is the DDM 2710. The operator can then grasp and release objectsbetween forceps jaw 2750 and DDM 2710 by pushing or pulling on push rod2730.

FIG. 28, and FIGS. 29A through 29D depict another embodiment of a DDM.In practice, this embodiment has provided great differential action andrapid dissection through complex tissues. For this embodiment of a DDM,the projections of the tissue engaging surface are formed by valleys cutinto the surface of the DDM. Referring to FIG. 28, DDM 2800 has a firstend 2810 and a second end 2820, with a central axis 2825 connecting thefirst end 2810 and second end 2820. First end 2810 is directed away fromthe complex tissue to be dissected (not shown) and is engaged with adrive mechanism (not shown) that moves DDM 2800 such that second end2820 sweeps along a direction of motion. Here, the mechanism oscillatesDDM 2800 about an axis of rotation 2830 that is perpendicular to thecentral axis 2825 such that the direction of motion 2840 is an arc ofmotion lying in a plane perpendicular to the axis of rotation 2830. Thesecond end 2820 has a tissue-facing surface 2850 that is directed towardthe complex tissue comprising at least one tissue engaging surface 2860and at least one lateral surface 2870.

The motion of DDM 2800 in this example is a reciprocal (back-and-forth)oscillation, but other DDMs can have a continuous rotation or arectilinear motion. The rotation is preferably between 2,000 and 25,000cycles per minute, but can range from 60 cycles per minute up to 900,000cycles per minute, all of which are well below ultrasonic. In certainembodiments, speeds of 300 to 25,000 cycles per minute have been foundto be very effective.

FIGS. 29A through 29E show magnified views of the tissue-facing surface2850 of DDM 2800 from FIG. 28. FIG. 29A shows an oblique view oftissue-facing surface 2850 with components identified. FIGS. 29B-D showdifferent views of tissue-facing surface 2850 with the geometry of theshape better described, especially with respect to components oftissue-facing surface 2850. Finally, FIG. 29E show different embodimentsof some of these components. The tissue-facing surface 2850 has a tissueengaging surface 2860 and two lateral surfaces, a first lateral surface2871 disposed lateral to and to one side of the tissue engaging surface2860 and a second lateral surface 2872 disposed lateral to and to theopposing side of the tissue engaging surface. Referring to FIGS. 29A and29C, the tissue engaging surface 2860 is comprised of an alternatingseries of at least one valley 2910 and one projection 2920 arrayed alongthe direction of motion 2840 which is an arc of motion on thetissue-facing surface 2850 such that the intersection of the at leastone valley 2910 and at least one projection 2920 define at least onevalley edge 2930 oriented such that it has a component of directionperpendicular to the direction of motion 2840.

No valley edge 2930 should be sharp, e.g. it should not be capable ofslicing into Complex Tissue, especially into Firm Tissue. For example,no point on a valley edge 2930 should have a radius of curvature R_(c)smaller than approximately 0.025 mm (see FIG. 29C, expanded view). Thisradius of curvature R_(c) is similar to the radius of curvature of thesurface R_(s) and of the edge R_(e) as depicted in FIG. 15. We haveshown through testing that edges with radius of curvature R_(c) nosmaller than approximately 0.050 mm can be effective, too. Additionally,the radius of curvature R_(c) can vary along the length of valley edge2930. In the embodiment shown in FIGS. 29A through 29D, the radius ofcurvature R_(c) is smallest where the valley edge 2930 is furthest fromthe axis of rotation 2830 and increases closer to the first lateralsurface 2871 and the second lateral surface 2872. Furthermore, theminimum radius of curvature R_(c) for a valley edge 2930 can bedifferent for different valley edges in the same DDM and even for thevalley edges on opposing sides of the same valley.

Projections 2920 in DDM 2800 may be formed by subtractive manufacture inone embodiment. In effect, the valleys 2910 are cut out of the surfaceof a semi-ellipsoid, as shown in FIGS. 29B-C, having a major semi-axis Aaligned perpendicular to the rotational velocity 2830 and parallel tothe central axis 2825 (see FIG. 28) (i.e. pointing toward the ComplexTissue), a first minor semi-axis B, and a second minor semi-axis C thatis parallel to the rotational velocity 2830. The projections 2920 thushave projection tops 2940 that are the remaining semi-ellipsoidalsurface and are continuous with the lateral surfaces 2971 and 2972.Tissue engaging surfaces 2860 are thus created by the lateral limits ofthe valleys 2910 in this embodiment and span the tissue-facing surfacebetween the valleys 2910 that form the projection 2920. In otherembodiments, projections can be formed by other means and can thus havemore differently shaped projection tops, including projection tops thatare not formed as the remainder of a surface. For example, in oneembodiment, the projections can effectively be built up from a surface,enabling more complex projection tops.

Referring to FIG. 29A and FIG. 29C, each valley 2910 may have a firstvalley side 2911, a second valley side 2912, and a valley bottom 2913,whereby the first valley side 2911 and the second valley side 2912 lieon opposing sides of the valley 2910. The valley bottom 2913 is linearor curvilinear and can be two-dimensional or 3-dimensional. For example,the valley bottoms in DDM 2800 are straight lines aligned parallel tothe rotational velocity 2830. The first valley side 2911 and the secondvalley side 2912 rise from the valley bottom 2913 to a valley edge 2930.The transition from valley bottom can be gradual and indeterminate, asin the valleys 2910 in DDM 2800, or the transition can be faceted. Avalley 2910 may be curved in two dimensions, being straight in thedirection parallel to the valley bottom 2913 (and thus also parallel tothe axis of rotation 2830). Valley sides, however, can be any shape,including surfaces curved in three dimensions.

A valley edge is formed by the intersection of a valley wall with aprojection top. Valley edges can thus have different shapes, dependingon the shapes of the projection top and the valley edge. The valleyedges 2930 on DDM 2800 trace three dimensional curves and thus have bothcurvature and torsion (as defined mathematically in geometry) that arenon-zero and varying along the valley edge. Valley edges can havesmoothly varying curvature and torsion (as do valley edges 2930), or avalley edge can be bent.

FIG. 29C presents an expanded view of a valley edge, in the planeperpendicular to the valley edge. The projection top 2920 and the valleyside (2911 or 2912 here) form a face angle Γ in this plane that isrounded at the intersection (i.e. it is “radiused” as a machinist woulddescribe it) having the radius of curvature R_(c) described above. Theface angle Γ can form an angle less than 90°, which appears sharp onfirst inspection, but sharpness is determined by the radius of curvatureR_(c) of the edge. The face angle Γ can vary along the length of thevalley edge, as it does for DDM 2800 where the face angle Γ is smallestat the points on the valley edge furthest from the axis of rotation2830. In one embodiment, face angles of about thirty degrees (30°) toabout one hundred fifty degrees (150°) may be effective.

Valleys have a length, width, and depth where the valley length is thelength of the valley bottom, the valley width is the distance separatingthe valley edges of one valley measured at their longest distance ofseparation, and the valley depth is the maximum vertical distance from avalley edge to the valley bottom (e.g. peak-to-trough height). Typicaldimensions for a valley include valley lengths of 0.25 mm to 10 mm,valley widths of 0.1 mm to 10 mm, and valley depths of 0.1 mm to 10 mm.In one embodiment, a valley length of approximately three (3) mm, avalley depth of approximately three (3) mm, and a valley width ofapproximately two (2) mm has been found to be very effective.

When a DDM has multiple valleys, like DDM 2800, the valleys can beparallel, like valleys 2910 of DDM 2800, having valley bottoms 2913 thatare all parallel, or they can be non-parallel with valley bottoms lyingat non-zero angles with respect to each other or at variable angles withrespect to each other.

The valleys 2910 of DDM 2800 have a single channel (the space bounded bythe valley sides and valley bottom); however, valleys can have multiple,intersecting channels such that valley bottoms can fork or multiplybranch or form networks on the tissue engaging surface. FIG. 29E showsdepicts top views of two DDMs, the left DDM 2980 having parallel valleys2981 with valley bottoms that are not parallel to the rotationalvelocity while the right DDM 2990 has network 2991 of multipleintersecting valleys all at different angles with respect to therotational velocity and to each other.

As described above, the tissue-facing surface 2850 of DDM 2800 has thesurface of a semi-ellipsoid having a major semi-axis A alignedperpendicular to the axis of rotation 2830 and parallel to the centralaxis 2825, a first minor semi-axis B, and a second minor semi-axis Cthat is parallel to the axis of rotation 2830. Tissue-facing surface2850 may have an ellipsoid shape in one embodiment, in which A>B>C.However, any relationship is possible between the lengths of thesemi-axes. For example, in other embodiments, DDMs may be fabricated forwhich A=B=C (e.g., the tissue-facing surface is hemi-spherical).

The first lateral surface 2871 and the second lateral surface 2872 ofDDM 2800 are continuations of the hemi-ellipsoidal shape. As such, theylie at an angle to one another, forming a wedge, as earlier depicted inFIG. 19D and FIG. 20, that aligns and strains fibrous components of aComplex Tissue allowing the projections to snag and break the fibrouscomponents.

FIG. 30 presents the situation of a first tissue region 3011 encased infirst membrane 3016 and second tissue region 3012 encased in secondmembrane 3017. First membrane 3016 and second membrane 3017 abut attissue plane 3020. First membrane 3016 and second membrane 3017 areformed of densely packed fibrous components and thus comprise a FirmTissue. The interstitial materials spanning the tissue plane from firstmembrane 3016 to second membrane 3017 include fibrous components 3030.These fibrous components 3030 are less densely packed, so theinterstitial materials comprise a Soft Tissue. As tissue-facing surface2850 is pressed in the direction of arrow 3050 into the tissue plane3020 to separate the two tissue regions 3011 and 3012, the first lateralsurface 2871 and the second lateral surface 2872 exert a first spreadingforce 3041 and a second spreading force 3042 on tissue regions 3011 and3012, respectively, that align and strain fibrous components 3030 at theprojection tops 2940 (see FIG. 29C). This enables the fibrous components3030 to enter the valleys 2910 and thus be snagged and then torn by aprojection 2920 as the tissue-facing surface 2850 rotates about axis ofrotation 2830 and so moves out of the plane of the page (toward theviewer). Additionally, as the projection tops 2940 are continuous withthe lateral sides, the more lateral areas of the projection tops 2940also exert additional spreading forces 3043 and 3044 that also wedgetissue regions 3011 and 3012 apart, further increasing the strain onfibrous components 3030.

FIG. 30 also illustrates an important aspect of a DDM. A DDM willautomatically follow a tissue plane. Because tissue planes tend to bebounded by Firm Tissues (e.g. membranes, ducts, etc.) and are spanned bySoft Tissues, a DDM will, by virtue of its differential action, not moveinto the Firm Tissue and will move into the Soft Tissue, thus followingand separating a tissue plane will little or no guidance from anoperator. This means that the operator need not have as detailed anunderstanding of the anatomy as is required by current practice or,conversely, a DDM allows a skilled surgeon to more confidently dissectan uncertain anatomy, e.g. when tissue planes are distorted by a tumoror when tissues are swollen or inflamed.

FIG. 31 shows an end-on view of the tissue-facing surface 2850 as itsnags and then stretches to breaking the fibrous components 3030 shownin FIG. 30. Three fibrous components (first fibrous component 3031,second fibrous component 3032, and third fibrous component 3033) havebeen snagged by three projections (first projection 2921, secondprojection 2922, and third projection 2923, respectively). Tissue facingsurface 2850 rotates, generating a direction of motion 2840 which is anarc of motion as depicted by arrows 3100. First fibrous component 3031has just entered the first valley 2911 and has not yet been snagged byfirst projection 2921. Second fibrous component 3032 entered the secondvalley 2912 at an earlier point in time and has been snagged andstrained by second projection 2922. Third fibrous component 3033 enteredthe third valley 2913 at an even earlier point in time and has beensnagged and strained even further by third projection 2923. Ultimately,all three fibrous components 3031, 3032, and 3033 will be strained tobreaking.

FIG. 31 illustrates an important aspect of DDM 2800's design. Becausethe valleys span from one lateral surface 2871 to the opposing lateralsurface 2872, each valley creates an open space spanning across the endof DDM 2800 into which strained fibrous components can enter, thusfacilitating their being snagged by the projections.

It is important to note that DDM 2800 does not have arrays of smallprojections that give any part of its surface texture, as describedearlier. Rather, all surfaces of DDM 2800 are smooth and, preferably,possess low friction surfaces. The shapes and configurations of thesurface features of DDM 2800 are responsible for its ability todifferentially dissect Complex Tissues. In fact, DDM 2800 works bestwhen all of its surfaces that are in contact with tissue are welllubricated with, for example, a surgical lube.

FIG. 32 shows an exploded view of one embodiment of a completedifferential dissecting instrument. The differential dissectinginstrument 3200 is grossly comprised of an instrument handle 3212 fromwhich projects an instrument insertion tube 3290 which has a first end3291 attached to instrument handle 3212 and a second end 3293, to whichis rotatably mounted a DDM 3292. The instrument handle 3212 is assembledfrom an upper housing 3220, which includes upper battery cover 3222, anda lower housing 3230, which are held together by instrument housingbolts 3236. Included in the upper housing 3220 and lower housing 3230are a motor 3260 and a battery pack 3270. In the upper housing 3220 is aswitch port 3224, through which can be accessed a switch 3282 (which maybe a momentary switch or an on-off switch) for providing power to themotor 3260 from the battery pack 3270. A printed circuit board 3280further containing a power level adjustment 3281 (which can be anyconvenient component, but is here shown as a linear potentiometer) isprovided and can be accessed through a flexible switch cover 3284mounted in surface of the upper housing 3220. Also included are forwardspring battery connectors 3272 and aft spring battery connectors 3274,which route electric power from the battery pack 3270. The upper housing3220 further contains an instrument insertion tube support 3226 tosecure and orient the instrument insertion tube 3290 near and coaxialwith the motor 3260.

The lower housing 3230 further provides access to and secures thebattery pack 3270 with an integral lower battery cover 3232 and motorhousing section 3234, further held to the upper housing 3220 using thethree instrument housing bolts 3236. The motor housing section 3234holds and secures the motor 3260 coaxial with the instrument insertiontube 3290, which passes through the instrument insertion tube support3226. The motor 3260 is pressed forward by the motor housing section3234 against the motor collar 3264, the inside diameter of which leavesroom for the motor shaft coupler 3262. The motor shaft coupler 3262,with the help of the motor shaft coupler bolts 3266, mounts securelyonto the end of the shaft of the motor 3260 and further grips a firstend 3295 of a drive shaft 3294. The drive shaft 3294 is rotated by themotor 3260 inside of and concentrically with the instrument insertiontube 3290. The drive shaft 3294 also has a second end 3297 of driveshaft 3294, which is concentrically supported by a shaft bearing 3296that is mounted onto a second end 3293 of instrument insertion tube3290. The DDM 3292 is rotatably mounted onto shaft bearing 3296 suchthat drive shaft 3294 causes DDM 3292 to rotate. DDM 3292, shaft bearing3296, drive shaft 3294, and instrument insertion tube 3290 collectivelyform the DDM assembly 3299, which is described next.

FIG. 33A, FIG. 33B, and FIG. 33C depict the details of the DDM assembly3299, including how the DDM 3292 is assembled with other components suchthat the motor 3260 drives oscillation of DDM 3292.

Referring now to FIG. 33A, DDM 3292 in this embodiment comprises atissue facing surface 3322 on a first end 3321 and a shaft bearing grip3324 on a second end 3323. The shaft bearing grip 3324 is further fittedwith two pivot pins 3325. The DDM 3292 may be partially hollow,possessing a shaft bearing cavity 3326 that permits the shaft bearing3296 to fit inside. The shaft bearing cavity 3326 further sports a camfollowing cavity 3328. The shape of the cam following cavity 3328 may beoblong in that it is much narrower in one direction, forming a slot.Shaft bearing 3296 has a bore 3336, a shaft bearing tip 3332, a threadedbearing end 3338, and two pivot pin holes 3334. Threaded shaft bearingend 3338 screws into threaded shaft bearing mount 3342 on the second end3293 of instrument insertion tube 3290. Bore 3336 can have a diametergreater than the diameter 3385 of drive shaft 3294 everywhere along itslength, except at shaft bearing tip 3332, thereby decreasing the contactsurface between shaft bearing 3296 and drive shaft 3294. The second end3297 of drive shaft 3294 is modified to include a main shaft section3352 and a cam shaft section 3354. The various sub-components of thesecomponents allow for their assembly and operation, as can be seen inFIG. 33B and FIG. 33C.

Referring now to FIG. 33B, drive shaft 3294 is shown as fittingcoaxially within shaft bearing 3296 and instrument insertion tube 3290of the DDM assembly 3299. This aligns threaded bearing end 3338 of shaftbearing 3296 for screwing into the threaded shaft bearing mount 3342located at the second end 3293 of instrument insertion tube 3290. Ashaft bearing tip 3332 accommodates drive shaft 3294, preventingmisalignment with respect to the DDM 3292. The second end 3293 of driveshaft 3294 emits from shaft bearing tip 3332 such that cam shaft section3354 is fully exposed. Once the instrument insertion tube 3290, shaftbearing 3296, and drive shaft 3294 are assembled, the DDM 3292 mountsonto shaft bearing 3296 such that (a) the pivot point pins 3325 insertinto pivot pin holes 3334 and (b) cam shaft section 3354 inserts intocam following cavity 3328, as shown in FIG. 33C.

FIG. 33C depicts the assembled DDM assembly 3299. The DDM 3292 fits overthe shaft bearing 3296, which is screwed into the threaded shaft bearingmount 3342 of the instrument insertion tube 3290, all of which coaxiallyencompass the drive shaft 3294. It is notable that the pivot pins 3325on the shaft bearing grip 3324 fit into the pivot pin holes 3334 of theshaft bearing 3296. This arrangement, combined with the shaft bearingcavity 3326, allows the hollow DDM 3292 to rotate freely on the pivotpins 3325. Rotation of drive shaft 3294 causes cam shaft section 3354 torotate inside cam following cavity 3328, driving DDM 3292 to oscillateabout the pivot pin holes 3334 and sweeping tissue facing surface 3322side-to-side as indicated by double sided arrow 3377.

In operation, referring to FIG. 32 and FIGS. 33A through 33C, a surgeonholds the differential dissecting instrument 3210 by the instrumenthandle 3212 and orients the distal tip sporting the DDM 3292 toward thecomplex tissue to be dissected. The surgeon selects the power level bysliding the power level adjustment 3281 to the desired position and thenplaces his or her thumb upon the switch 3282 and presses it to close theswitch. When switch 3282 closes, motor 3260 is turned on and rotates themotor shaft coupler 3262 and, in turn, the drive shaft 3294. The driveshaft 3294 is held coaxially and quite precisely in place by the shaftbearing 3296 and especially the shaft bearing tip 3332, so that the camshaft section 3354 of the drive shaft 3294 oscillates rotationallyinside the cam following cavity 3328 of the shaft bearing cavity 3326 ofthe DDM 3292. The cam following cavity 3328 is oblong, and in theembodiment shown in FIGS. 33A through 33C has its narrowest dimensionoccurring in the direction perpendicular to the axis of the rotationaljoint formed by the pivot pins 3325 and the pivot pin holes 3334. Inthis embodiment, the narrowest dimension of the cam following cavity3328 just barely permits the passage of the cam shaft section 3354 ofthe now rotating drive shaft 3294. Accordingly, the rotationaloscillation of the cam shaft section 3354 impinges on the long walls ofthe cam following cavity 3328, forcing the entire DDM 3292 to rotatethrough an oscillation arc 3377 lying in a plane perpendicular to theaxis of the rotational joint formed by the pivot pins 3325 and the pivotpin holes 3334. In this embodiment, the amplitude of the oscillation arc3377 through which the tissue facing surface 3322 of the differentialdissecting member 3292 swings is a function of the diameter 3385 of thedrive shaft 3294 out of which the cam shaft section 3354 is cut and thedistance 3379 separating tissue facing surface 3322 and pivot pin holes3334. The frequency of the oscillation matches the frequency of theoscillation of rotation of the motor 3260. The operator may control theoscillation frequency of the tissue facing surface 3322 by varying theposition of the power level adjustment 3281. Note that this mechanismfor converting rotation of motor 3260 and thus rotation of drive shaft3294 into oscillation of the DDM 3292 is similar to the scotch yokedepicted in FIGS. 22 through 25C.

Differential Dissecting Instrument 3200 is one example of implementationof a DDM, and many variants are possible. For example, oscillation of aDDM can be driven by a crank and slider mechanism with the slider movingback-and-forth longitudinally inside an instrument insertion tube.Alternatively, a motor could be placed adjacent to the DDM, with themotor shaft directly driving the DDM and only electrical wires to powerthe motor running down the instrument insertion tube. Additionally,because a DDM adapts well to the end of a tube, greatly lengthening theinstrument insertion tube allows differential dissecting instruments,such as Differential Dissecting Instrument 3200, for example, to belaparoscopic instruments. Differential Dissecting Instruments withinstrument insertion tubes as long as thirty-six (36) cm may be used,although longer or shorter tubes are easily accommodated in the design.DDMs as disclosed herein can easily be adapted to the arm of a surgicalrobot, such as the Da Vinci Surgical Robot from Intuitive Surgical(Sunnyvale, Calif.). A DDM can be made very small; for example,effective Differential Dissecting Instruments in which the DDM andinstrument insertion tube fit through a five (5) mm hole, such as asurgical port, can be built, enabling minimally invasive surgery. Thesesmaller devices are easily built.

Further, Differential Dissecting Instruments can be used in which thedrive shaft is replaced by a flexible drive shaft, and the instrumentinsertion tube is curved. This creates Differential DissectingInstruments with curved instrument insertion tubes, like that shown inFIG. 6C. Articulation of the instrument insertion tube is also possible,using for example a drive shaft having a universal joint or otherbendable coupler at the articulation.

As previously disclosed, additional functionality can be added to theend of a Differential Dissecting Instrument. For example,

-   -   FIG. 11B and FIG. 13 show how the design of the DDM permits        fluids to be delivered to a DDM for irrigation, or how suction        can be applied to clear the surgical field, or how a light        source can be placed on or near a DDM to illuminate the surgical        field.    -   FIG. 26A through FIG. 26D disclose a Differential Dissecting        Instrument having an retractable cutting blade that can be made        sharp for cutting or can be energized by a electrosurgical        generator (unipolar or bipolar) for electrosurgery,    -   FIG. 27A and FIG. 27B show how the design of the DDM permits a        DDM to be adapted to function as forceps.

Additional functionality can readily be added to a DifferentialDissecting Instrument. For example, a patch of any size on the side of aDDM or a shroud holding a DDM can be energized such that the patch canbe used for electrocautery. To simplify fabrication, the drive shaft canbe used to conduct the electricity from the handle to the DDM. Thedesign of the DDM permits the forceps shown in FIG. 27B to instead beused as scissors. The improved design of the DDM permits many of theseadditional functionalities to be combined together in one DifferentialDissecting Instrument. Advantages realized from combiningfunctionalities with a DDM at the working end of a DifferentialDissecting Instrument include: reducing the number of instruments asurgeon needs for a procedure; simplifying inventory for the hospitaland logistics for support staff; and, most importantly, reducinginstrument changes during surgery, which slow surgery and are a majorsource of surgical complications. This is especially true inlaparoscopic and robotic surgeries, which require positioninginstruments into the body through small incisions, frequently withairtight ports.

FIG. 34 shows an oblique view of one embodiment of an assembledDifferential Dissecting Instrument. The Differential DissectingInstrument 3400 is grossly comprised of an instrument handle 3412 fromwhich projects an instrument insertion tube 3490 which has a first end3491 attached to instrument handle 3412 and a second end 3493, to whichis rotatably mounted a DDM 3492. The instrument handle 3412 is assembledfrom an upper housing 3420, which includes upper battery cover 3422, anda lower housing 3430, which includes lower battery cover 3432. Enclosedin the upper housing 3420 and lower housing 3430 are a motor 3460 andbatteries 3470, which can, optionally, be assembled into a battery pack.In the upper housing 3420 is a switch 3482 (which may be a momentaryswitch or an on-off switch) for providing power to the motor 3460 fromthe battery pack 3470. A flexible switch cover 3484 mounted in thesurface of the upper housing 3420 allows access to the power leveladjustment 3581 (FIG. 35A) inside. The upper housing 3420 furthercomprises a retractable blade hook control button 3499 (secured by acontrol button bolt 3498), as well as an instrument insertion tubesupport 3426 to orient the instrument insertion tube 3490 near andcoaxial with the motor 3460.

FIG. 35A shows an exploded view of Differential Dissecting Instrument3400. The Differential Dissecting Instrument 3400 is grossly comprisedof an instrument handle 3412 from which projects an instrument insertiontube 3490 which has a first end 3491 attached to instrument handle 3412and a second end 3493, to which is rotatably mounted a DDM 3492. Theinstrument handle 3412 is assembled from an upper housing 3420, whichincludes upper battery cover 3422, and a lower housing 3430, whichincludes a lower battery cover 3432, which are held together byinstrument housing bolts 3536. Included within the upper housing 3420and lower housing 3430 are a motor 3460 and batteries 3470, here shownas battery type CR123A (3V each, 18V for all 6 batteries 3470) but otherbattery types and voltages can be used. We've used batteries totaling aslow as 3V in some embodiments. In the upper housing 3420 is a switchport 3524, through which can be accessed switch 3482 (which may be amomentary switch or an on-off switch) for providing power to the motor3460 from the battery pack 3470. A printed circuit board 3580 furthercontaining a power level adjustment 3581 (which can be any convenientcomponent, but is here shown as a linear potentiometer) is provided andcan be accessed through a flexible switch cover 3484 mounted to thesurface of the upper housing 3420. Also included are forward springbattery connectors 3572 and aft spring battery connectors 3574, whichroute electric power from the batteries 3470. The upper housing 3420further contains an instrument insertion tube support 3426 to secure andorient the instrument insertion tube 3490 near and coaxial with themotor 3460. An instrument insertion tube retaining bolt 3527 holds theinstrument insertion tube 3490 securely in the instrument insertion tubesupport 3426.

The lower housing 3430 further provides access to and secures thebatteries 3470 with an integral lower battery cover 3432 and motorhousing section 3534, further held to the upper housing 3420 using thethree instrument housing bolts 3536. The motor housing section 3534holds and secures the motor 3460 coaxial with the instrument insertiontube 3490, which passes through the instrument insertion tube support3426. The motor 3460 is pressed forward by the motor housing section3534 against the motor spring 3562, the inside diameter of which leavesroom for the motor shaft coupler 3562. The motor shaft coupler 3562,with the help of the motor shaft coupler bolts 3566, mounts securelyonto the end of the shaft of the motor 3460 and further grips a firstend 3595 of a drive shaft 3494. The motor 3460 can slide longitudinallyfore and aft within the motor housing section 3534 under the control ofthe retractable blade hook control button 3499. The motor 3460 furthercomprises a power contact plate 3569 which operably slides againstsprung motor power contacts 3563 mounted on circuit board 3580. Alsomounted on circuit board 3580 is an adjustable power contact pressurecontrol bolt 3561. Normally, spring 3567 keeps motor 3460 aft. In thatposition, the sprung motor power contacts 3563 mounted on the printedcircuit board 3580 are aligned with and press against the power contactplate 3569 on motor 3460, and so electric power from battery pack 3470can drive motor rotation. Pressing the retractable blade hook controlbutton 3499 forward causes motor 3460 to slide forward. The powercontact plate 3569 is shorter than the full extent of travel of motor3460 under the influence of retractable blade hook control button 3499,such that electric power from battery pack 3470 is automatically cut offwhen the motor 3460 is slid sufficiently far forward toward insertiontube second end 3493 to break contact with sprung motor power contacts3563.

The drive shaft 3494 also has a second end 3597, which passes throughand is concentrically supported by a shaft bearing 3496 that is mountedonto the second end 3493 of instrument insertion tube 3490. Referringalso to FIG. 35 B, the second end 3597 of drive shaft 3494 furthercomprises (from the tip of second end of 3597 and working inward) a camreceiver retainer 3555, a cam receiver driver 3554, and a shaft bearingclearance section 3552. DDM 3492 is rotatably mounted onto shaft bearing3496 such that drive shaft 3494 causes DDM 3492 to rotate with areciprocal oscillation. DDM 3492, shaft bearing 3496, a cam receiver3596, a cam receiver retainer 3555, drive shaft 3494, and instrumentinsertion tube 3490 collectively form the DDM assembly 3598, which isdescribed next.

FIG. 35B depicts the details of DDM assembly 3598, including how DDM3492 is assembled with other components such that the motor 3460 drivesreciprocal oscillation of DDM 3492. DDM 3492 in this embodimentcomprises a tissue facing surface 3522 on a first end 3521 and a shaftbearing grip 3524 on a second end 3543. The shaft bearing grip 3524 isfurther fitted with two pivot pin holes 3525. The DDM 3492 may bepartially hollow, possessing a shaft bearing cavity 3526 that permitsthe shaft bearing 3496 to fit inside. The shaft bearing cavity 3526further sports a cam receiver cavity 3548 shaped to permit cam receiver3596 to easily slide therein. In this embodiment, tissue facing surface3522 of DDM 3492 further comprises a retractable blade slot 3506. Shaftbearing 3496 has a bore 3536, a shaft bearing tip 3532, a threadedbearing end 3538, and two insertable pivot pins 3535 that fit intothreaded holes 3534. The threaded shaft bearing end 3538 screws intothreaded shaft bearing mount 3542 on the second end 3493 of instrumentinsertion tube 3490. Bore 3536 can have a diameter greater than thediameter 3585 of drive shaft 3494 everywhere along its length, except atshaft bearing tip 3532, thereby decreasing the contact surface betweenshaft bearing 3496 and drive shaft 3494. Second end 3497 of drive shaft3494 is modified to include main shaft section 3552, cam shaft section3554, and cam receiver retainer 3555. Cam receiver 3596 furthercomprises a cam receiver body 3502, a cam receiver chamber 3505, and aretractable blade 3501. Retractable blade can further comprise a hook3504 and a tissue engaging surface 3503. The various sub-components ofthese components allow for their assembly and operation, as is disclosedelsewhere in this document.

DDM 3492 fits over shaft bearing 3496, which is screwed into threadedshaft bearing mount 3542 of the instrument insertion tube 3490, all ofwhich coaxially encompass drive shaft 3494. It is notable that pivot pinholes 3525 on shaft bearing grip 3524 fit onto pivot pins 3535 of shaftbearing 3496. This arrangement, combined with shaft bearing cavity 3526,allows DDM 3492 to rotate freely on the pivot pins 3535. Rotation ofdrive shaft 3494 causes cam shaft section 3554 to rotate inside camreceiver 3596, driving DDM 3492 to reciprocally oscillate about thepivot pin holes 3525 and sweeping tissue facing surface 3522side-to-side.

In operation, a surgeon holds the differential dissecting instrument3400 by the instrument handle 3412 and orients the distal tip sportingthe DDM 3492 toward the complex tissue to be dissected. The surgeonselects the power level by sliding the power level adjustment 3581 tothe desired setting and then places his or her thumb upon the switch3482 and presses it to close the switch. When switch 3482 closes, motor3460 is turned on and rotates the motor shaft coupler 3562 and, in turn,the drive shaft 3494. The drive shaft 3494 is held coaxially and quiteprecisely in place by the shaft bearing 3496 and especially the shaftbearing tip 3532, so that the cam shaft section 3554 of the drive shaft3494 oscillates rotationally inside the cam receiver chamber 3505 of camreceiver 3502 captured within the DDM 3492. The rotational oscillationof the cam shaft section 3554 impinges on the walls of the cam receiverchamber 3505 of cam receiver 3502 which is configured as a scotch yokeas described earlier, forcing the entire DDM 3492 to rotate through anoscillation arc lying in a plane perpendicular to the axis of therotational joint formed by the pivot pins 3535 and the pivot pin holes3525. The surgeon can extend retractable blade 3501 by pushingretractable blade hook control button 3499 forward. Forward motion ofretractable blade hook control button 3499 causes motor 3460 and powercontact plate 3569 to move forward, separating power contact plate 3569from sprung motor power contacts 3563 and cutting power to the motor, asdescribed earlier, and preventing oscillation of DDM 3492.Simultaneously, forward motion of motor 3460 pushes drive shaft 3494forward, toward second end 3493 of instrument insertion tube 3490.Forward motion of drive shaft 3494 in turn pushes cam receiver retainer3555 against the top of cam receiver chamber 3505 inside cam receiverbody 3502, thereby pushing cam receiver body 3502 further up camreceiver cavity 3548 and extending retractable blade 3501 out ofretractable blade slot 3506. Thus, forward motion of retractable bladehook control button 3499 causes the motor 3460 to stop and retractableblade 3501 to extend out of DDM 3492. When retractable blade hookcontrol button 3499 is released, motor spring 3562 pushes motor 3460aft, retracting retractable blade 3501 and restoring electrical contactsfor the motor.

In this embodiment the amplitude of the oscillation through which thetissue facing surface 3522 of the differential dissecting member 3492swings is a function of the diameter 3585 of the drive shaft 3494 out ofwhich the cam shaft section 3554 is cut and the distance 3579 separatingtissue facing surface 3522 and pivot pin holes 3525. The frequency ofthe reciprocal oscillation (cycles per minute) of the DDM 3492 againstthe complex tissue matches the frequency of rotation (rotations perminute) of the motor 3460. The operator may control the oscillationfrequency of the tissue facing surface 3342 by varying the position ofthe power level adjustment 3581. Note that this mechanism for convertingrotation of motor 3460 and thus rotation of drive shaft 3494 intooscillation of the DDM 3492 is similar to the scotch yoke depicted inFIGS. 22 through 25C.

FIG. 35C illustrates that fore/aft motion of drive shaft 3494 and, thusof cam receiver body 3502, also alters the amplitude of reciprocaloscillation of DDM 3492. Drive shaft 3494 is depicted in the aftposition (having moved in the direction of arrow 3595) in the left frameof FIG. 35C and in the fore position (having moved in the direction ofarrow 3597) in the right frame. Thus, as cam receiver body 3502 movesforward inside cam receiver cavity 3548, the distance D from camreceiver body 3548 and pivot pin holes 3525 increases to D′ while thelateral displacement of the receiver 3599 remains constant (because itis determined by the diameter 3585 of drive shaft 3494, as describedabove). As D′ increases, the larger angular amplitude of DDM 3596 in theleft frame decreases to the smaller angular amplitude of DDM 3598 in theright frame. This effect can be used to decrease the amplitude ofoscillation when a retractable blade is extended. It can also be used toalter the amplitude of oscillation during blunt dissection by the DDM,for example when a surgeon wants a narrower oscillation for more precisedissection.

FIGS. 36A and 36B show the end of a Differential Dissecting Instrument3600 having a DDM 3610 rotatably mounted to instrument insertion tube3620 via rotational joint 3630. Differential Dissecting Instrument 3600also has a retractable hook 3640 that can be extended or retracted bymotion in the direction indicated by double headed arrow 3650.Retractable hook 3640 can be retracted or extended using, for example,the mechanism described in FIGS. 34, 35A, and 35B. FIG. 36A demonstrateshow retractable hook 3640 can be placed into two configurations.CONFIGURATION 1 shows retractable hook 3640 in the extended position,and CONFIGURATION 2 shows retractable hook 3640 in the retractedposition. Retractable hook 3640 can have a tip 3670 that can be pointedor rounded and a tissue engaging surface 3660 that can be moreaggressive than tissue engaging surface 3690 of DDM 3610, or it can beless aggressive. Retractable hook 3640 possesses an elbow 3680 that canbe sharpened to slice, as shown here, or it can be dull; furthermore, itcan be serrated, and the sharpened region can be located anywhere withinthe elbow. In CONFIGURATION 2, retractable hook is hidden inside DDM3610, and DDM 3610 alone interacts with the tissue. In CONFIGURATION 1,retractable hook 3640 is exposed and can be used to interact with thetissue such that tissue engaging surface 3690 interacts with the tissue(e.g. to disrupt softer tissues), or such that tip 3670 interacts withtissue (e.g. to pierce a tissue), or elbow 3680 interacts with tissue(e.g. to slice a tissue), depending on how an operator positionsretractable hook 3640 with respect to the tissue. Additionally,retractable hook 3640 can be held at any intermediate position betweenCONFIGURATION 1 and CONFIGURATION 2, including being able to be variablyextended by an operator.

FIG. 36B shows the end of a Differential Dissecting Instrument 3600 andillustrates that DDM 3610 can oscillate with retractable hook in theextended configuration (CONFIGURATION 1) or the retracted configuration(CONFIGURATION 2) and that retractable hook 3640 can be retracted orextended before activation of oscillation of DDM 3610 or duringoscillation of DDM 3610. Arrow 3601 shows retractable hook movingbetween the retracted configuration (lower left frame) to the extendedconfiguration (upper left frame) while DDM 3610 is not oscillating.Arrow 3602 shows that DDM 3610 can be switched from stationary (upperleft frame) to oscillating (upper right frame) while retractable hook3640 is in the extended configuration. Arrow 3603 shows that retractablehook 3640 can be moved from the extended configuration (upper rightframe) to the retracted configuration (lower right frame) while DDM 3610is oscillating. Arrow 3604 shows that DDM 3610 can change fromstationary (lower left frame) to oscillating (lower right frame) whileretractable hook 3640 is in the retracted configuration. Retractablehook 3640 can optionally be made of an electrically conductive material,like stainless steel, and electrically connected to an external surgicalelectrosurgical generator to allow retractable hook 3640 to act as anelectrosurgical hook.

Many tissues to be dissected are wrapped in a membrane or capsule that asurgeon must divide to gain access to that tissue. Once that membrane orcapsule has been divided, the surgeon proceeds with dissection throughthat tissue. FIG. 37 illustrates in four panels a method by which aDifferential Dissecting Instrument 3600 can be used to safely andquickly divide a membrane 3710 overlying a tissue 3700, such as theperitoneum overlying the gall bladder or the capsule surrounding aliver. In the upper left panel, the Differential Dissecting Instrumentis seen approaching membrane 3710 with the retractable hook 3640 in theextended configuration. In the upper right panel, the tissue engagingsurface 3660 of retractable hook 3640 is pressed by the surgeon againstmembrane 3710, and the DDM 3610 is oscillated such that tissue engagingsurface 3660 abrades membrane 3710. (Alternatively, the retractable hook3640 can be held in the retracted configuration, and the tissue engagingsurface 3690 of DDM 3610 can be used to abrade membrane 3710. If the twotissue engaging surfaces 3660 and 3690 have different levels ofaggressiveness, the surgeon then has the flexibility of choosing eitherthe more aggressive or the less aggressive tissue engaging surface toabrade the membrane 3710.) The tissue is abraded until a small opening3720 is made in membrane 3710. Next, as shown in the lower left panel,the surgeon then pries the tip 3670 of retractable hook 3640 throughopening 3720 and under membrane 3710, lifting or “tenting” a flap 3730of membrane 3710 away from tissue 3700. The surgeon then moves DDM 3600in the direction of arrow 3740, thereby forcing flap 3730 into the elbow3680 of retractable hook 3640, the elbow 3680 being sharpened to slicetissue. Finally, as shown in the lower right panel, the surgeon makesDDM 3610 oscillate, causing retractable hook 3640 to oscillate and,thus, the sharp edge of the elbow 3680 of retractable hook 3640 toquickly move into membrane 3710 as the surgeon continues moving DDM 3600in the direction of arrow 3740. This has been demonstrated with freshtissues to be an easy, quick, and safe way to divide a membrane, such asthe peritoneum overlying the gall bladder and bile duct, withoutdamaging underlying structures (e.g. the gall bladder, bile duct, orliver). The tip 3680 of retractable hook 3640 can be made sufficientlyblunt that it does not easily penetrate the membrane 3710 or underlyingstructures; furthermore, the placement of the sharp edge only at elbow3680 prevents critical structures from being exposed to the sharp edge3680 and thus reducing the likelihood of such critical structures beingcut. Examples of membranes or capsules overlying critical structuresinclude the peritoneum overlying the liver, gall bladder, cystic duct,and cystic artery; and the pleura overlying the lung, pulmonary artery,pulmonary vein, and bronchus.

A retractable hook can be used in a method similar to that shown in FIG.37 to dissect tougher fibrous structures, like adhesions, fibroustissues surrounding the renal artery or vein, and scar tissue. Forexample, a surgeon can use the tip of a retractable hook to grab all ora portion of a fibrous structure and then can push the tissue into thesharpened elbow of the hook. The surgeon can then oscillate the DDM andhook to use the sharp edge inside the hook to cut the tissue. Anadvantage of this approach is that it applies the stresses in theimmediate location of the tissue to be divided. In current practice,surgeons divide such tissues by a variety of techniques, includingsimply grabbing the sides or ends of such tissues and pulling them untilthey break. This can at times put large stresses on the tissues beingpulled, such as the wall of the intestine, leading to accidental tearingof critical tissues, such as the wall of the intestine (and therebyperforating the bowel). By applying the stresses more locally anddirectly to the tissue to be divided (specifically at the sharpenedelbow of the hook), and not over larger expanses of tissues (e.g.between two pairs of forceps), a surgeon can have greater certainty thata more distant tissue, like the wall of the intestine, is unharmed.

It is important to note that these methods of dividing tissues by usinga hook that is oscillated does not heat the tissues, in stark contrastto the extreme heat that arises from current practice usingelectrosurgery. The heat from electrosurgery is widely acknowledged as amajor risk leading to accidental thermal damage of surrounding tissues.Competing technologies for sharp dissection, such as ultrasonic ablation(e.g. the “harmonic shears” from Ethicon Endosurgery), have beendeveloped to reduce the heat and thereby decrease the risk of thermaldamage to tissues. Nevertheless, local heating remains significant andthe risk of thermal damage is still present. On the contrary, dividing amembrane or dissecting a fibrous structure as described here with anoscillating hook causes no heating of tissues, eliminating this majorsource of iatrogenic trauma.

FIG. 38 shows one embodiment of a Differential Dissecting Instrument3800 for laparoscopic surgery. It uses the mechanism for oscillation ofthe DDM 3810 shown in FIGS. 34, 35A and 35B, including a retractableblade (not visible in this picture because it is in the retractedconfiguration). Differential Dissecting Instrument 3800 uses apistol-style handle 3820 having a trigger 3830 to start/stop oscillationof the DDM 3810 and a speed control 3840 for controlling the speed ofoscillation. A thumb-activated push-button 3850 is used to extend theretractable blade which is held in a normally retracted configuration bya spring mechanism inside handle 3820. A rotational wheel 3860 can bereached and turned with an index finger, and rotation of rotationalwheel 3860 rotates instrument insertion tube 3870 and attached DDM 3810such that the plane of oscillation 3880 of DDM 3810 can be easily turnedthrough 360 degrees, thereby allowing a surgeon to orient the plane ofoscillation 3880 with a tissue plane inside the body while maintaininggood ergonomics for the handle 3820. An indicator 3862 on rotationalwheel 3860 provides the surgeon with a visual cue outside the body as tothe orientation of the plane of oscillation 3880, and, similarly, visualcues, such as embossed stripes, can be placed on the instrumentinsertion tube 3870 or on DDM 3810 thereby providing a visual cue oncamera during laparoscopic viewing. An electrical plug 3890 allowsoptional attachment via cable to an external electrosurgical generatorfor electrosurgery and electrocautery (controlled by external footpedals attached to the electrosurgical generator for control of theelectrosurgical generator or, alternatively, push buttons (not shown)can be placed onto handle 3820 and used for control of theelectrosurgical generator). Differential Dissecting Instrument 3800,therefore, allows a surgeon to perform blunt dissection (viadifferential dissection), sharp dissection (via retractable hook orelectrosurgery), and coagulation (via electrocautery) with a singleinstrument, thereby reducing instrument changes which is complicated forlaparoscopic surgery.

FIG. 39 shows a Differential Dissecting Instrument 3900 configured as atool to be attached to the arm of a surgical robot, such as the da VinciRobot from Intuitive Surgical, Inc. DDM 3610 is rotatably attached toinstrument insertion tube 3910 via rotational joint 3630. Retractablehook 3640 can move between retracted and extended configurations, asindicated by double headed arrow 3650. Retractable hook 3640 has atissue engaging surface 3660, tip 3670, and elbow 3680 with a sharpenededge for sharp dissection. Retractable hook 3640 can, optionally, beelectrically conductive and electrically connected to an externalelectrosurgical generator. Similarly, DDM 3610 or a small electricallyconductive patch 3925 on DDM 3610 can be used for electrocautery. (Notethat an electrically conductive patch can be placed anywhere on DDM3610, including the tissue engaging surface 3690.) Instrument insertiontube 3910 attaches to housing 3920 which contains a motor to driveoscillation of DDM 3610 and retractable hook 3640 as described earlier.Housing 3920 is configured with socket 3930 having electrical andmechanical connections for connecting to the surgical robot's arm.Instrument insertion tube 3910 can be made long, such that housing 3920is located outside the patient's body. Conversely, instrument insertiontube 3910 can be made short, such that housing 3920 is located insidethe body, with articulations located in the robot arm and inside thepatient's body to permit articulated motion of Differential DissectingInstrument 3900 inside the patient's body.

Placement of a small motor in a housing closer to a DDM and inside thepatient's body facilitates articulation of the instrument insertion tubeof a Differential Dissecting Instrument because all connections from thehousing to the handle or housing, and thus through the articulation, canbe electrical, which can be much simpler than designs requiring thetransmission of mechanical drives through an articulation. This is truefor Differential Dissecting Instruments designed both for surgicalrobots and for laparoscopy. FIG. 40 shows one embodiment of such adevice as the end of a laparoscopic Differential Dissecting Instrument4000. A DDM 3610 is fitted with a retractable hook 3640 and electricallyconducting patch 3625. DDM 3610 is rotatably attached to distalinstrument insertion tube 4010 which is articulated at rotational joint4030 to proximal instrument insertion tube 4020. Mounted inside distalinstrument insertion tube 4010 are a motor 4040 with motor shaft 4050and a solenoid 4060 with solenoid plunger 4070. Rotation of motor shaft4050 by motor 4040 drives oscillation of DDM 4010 and, thus, retractablehook 3640, as described earlier. Solenoid 4060 is rigidly attached todistal instrument insertion tube 4010, and solenoid plunger 4070 isattached to motor 4040, which is free to slide inside distal insertiontube 4010. Thus, when solenoid 4060 is activated, solenoid plunger movesup/down (in the direction indicated by arrow 4080) thereby driving motor4040, motor shaft 4050, and retractable hook 3640 up/down (as indicatedby arrows 4080). Flexible conductor ribbon 4090 supplies the necessaryelectrical power and signals to drive motor 4040 and solenoid 4060.Articulation of laparoscopic Differential Dissecting Instrument 4000 atrotational joint 4030 allows distal instrument insertion tube 4010 tobend with respect to proximal instrument insertion tube 4020, as shownin the right hand panel. Motion of distal instrument insertion tube 4010with respect to proximal instrument insertion tube 4020 can be driven byany of several mechanisms, such as a control horn driven by a push-pullrod actuated by a hand-powered mechanism in the handle of thelaparoscopic Differential Dissecting Instrument 4000. This configurationof actuators (i.e. motor 4040 and solenoid 4060) and flexible conductorribbon 4090 facilitates the transmission of complex actions pastarticulation at rotational joint 4030, transmission that would otherwiserequire complex mechanical parts that are expensive, add bulk, and areprone to failure.

The embodiments set forth herein are examples and are not intended toencompass the entirety of the invention. Many modifications andembodiments of the inventions set forth herein will come to mind to oneskilled in the art to which these inventions pertain having the benefitof the teaching presented in the foregoing descriptions and theassociated drawings. Therefore, it is to be understood that theinventions are not to be limited to the specific embodiments disclosedand that modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areused herein, they are used in a generic and descriptive sense only andnot for the purposes of limitation.

We claim:
 1. A differential dissecting instrument for differentiallydissecting complex tissue comprising: a handle; an elongate memberhaving a first end and a second end, the first end connected to thehandle; a differential dissecting member configured to be rotatablyattached to the second end, the differential dissecting membercomprising at least one tissue engaging surface; a mechanism configuredto mechanically rotate the differential dissecting member around an axisof rotation thereby causing the at least one tissue engaging surface tomove in at least one direction against the complex tissue; wherein theat least one tissue engaging surface is configured to selectively engagethe complex tissue such that when the differential dissecting member ispressed into the complex tissue, the at least one tissue engagingsurface moves across the complex tissue and the at least one tissueengaging surface disrupts at least one soft tissue in the complextissue, but does not disrupt firm tissue in the complex tissue, whereinthe differential dissecting member has a first end and a second end;wherein the first end of the differential dissecting member isconfigured to be directed away from the complex tissue and is rotatablyengaged with the mechanism such that the differential dissecting memberand thus the second end of the differential dissecting member is rotatedby the mechanism; and wherein the second end of the differentialdissecting member is configured to be directed toward the complextissue, the second end of the differential dissecting member comprisinga semi-ellipsoid shape defined by three orthogonal semi-axes, the threeorthogonal semi-axes comprising a major semi-axis A, a first minorsemi-axis B, and a second semi-minor axis C, wherein the major semi-axisA is perpendicular to the axis of rotation, the second semi-minor axis Cis parallel to the axis of rotation, and the first minor semi-axis B isperpendicular to both the major semi-axis A and the second semi-minoraxis C.
 2. The differential dissecting instrument of claim 1, whereinthe tissue engaging surface further comprises projections that extendoutward from the tissue engaging surface, wherein the projections areconfigured to sweep through any gel-like material that covers tightlypacked, organized arrays of fibrous components that are part of the firmtissue, the projections further configured to snag and tear looselypacked fibrous components of the soft tissue, but to slip off of, andnot snag, the tightly packed, organized arrays of fibrous components inthe firm tissue.
 3. The differential dissecting instrument of claim 2,wherein the projections have a projection length of less than one (1)millimeter (mm).
 4. The differential dissecting instrument of claim 2,wherein the projections have a projection length of less than five (5)millimeters (mm).
 5. The differential dissecting instrument of claim 1,wherein the differential dissecting member further comprises athree-dimensional surface having no sharp edges such that thedifferential dissecting member will not slice the complex tissue.
 6. Thedifferential dissecting instrument of claim 5, wherein the differentialdissecting member has no edge having a radius of curvature smaller than0.05 millimeters (mm).
 7. The differential dissecting instrument ofclaim 5, wherein the differential dissecting member has no edge having aradius of curvature smaller than 0.025 millimeters (mm).
 8. Thedifferential dissecting instrument of claim 1, wherein the differentialdissecting member further comprises at least one non-tissue engagingsurface that can contact but does not engage the complex tissue suchthat the components of the complex tissue are not disrupted.
 9. Thedifferential dissecting instrument of claim 8, wherein the non-tissueengaging surface is smooth.
 10. The differential dissecting instrumentof claim 1, further comprising: at least one additional surface disposedlaterally to the tissue engaging surface, wherein the at least oneadditional surface is configured to wedge apart the complex tissue asthe differential dissecting instrument is pressed into the complextissue, thereby straining and aligning fibrous components of the atleast one soft tissue perpendicular to the motion of the tissue engagingsurface and thereby facilitating tearing of the fibrous components bythe tissue engaging surface.
 11. The differential dissecting instrumentof claim 10, wherein the at least one additional surface comprises atleast one surface on a shroud surrounding at least a portion of thedifferential dissecting member.
 12. The differential dissectinginstrument of claim 10, wherein the at least one additional surfacecomprises at least one non-tissue engaging surface on the differentialdissecting member.
 13. The differential dissecting instrument of claim1, wherein the elongate member and the differential dissecting memberare oriented with respect to each other such that the elongate memberand the axis of rotation of the differential dissecting member form apresentation angle that is not zero, allowing the tissue engagingsurface to be applied to a particular point on the complex tissue. 14.The differential dissecting instrument of claim 1, wherein thedifferential dissecting member is configured to oscillate at speedsranging from sixty (60) to twenty thousand (20,000) cycles per minute.15. The differential dissecting instrument of claim 1, wherein thedifferential dissecting member is configured to oscillate at speedsranging from two thousand (2,000) to nine hundred thousand (900,000)cycles per minute.
 16. The differential dissecting instrument of claim1, wherein the major semi-axis A is longer than the first and secondminor semi-axes (A>B and A>C).
 17. The differential dissectinginstrument of claim 1, wherein the major semi-axis A, the first minorsemi-axes B, and the second minor semi-axis C all have different lengths(A≠B≠C).
 18. The differential dissecting instrument of claim 1, whereinthe differential dissecting member comprises a body; and furthercomprises the at least one tissue engaging surface distributed over atleast a portion of the outer surface of the body and having: a minimumplacement radius, R_(min), along a line perpendicular to the axis ofrotation measured from the axis of rotation to a point on the tissueengaging surface closest to the axis of rotation, a maximum placementradius, R_(max), along a line perpendicular to the axis of rotationmeasured from the axis of rotation to a point on the tissue engagingsurface furthest from the axis of rotation, and the minimum placementradius, R_(min), is greater than zero.
 19. The differential dissectinginstrument of claim 18, wherein the difference between the minimumplacement radius, R_(min), and the maximum placement radius, R_(max), isequal to or greater than 5% of R_(max), i.e.(R_(max)−R_(min))≧0.05*R_(max).
 20. The differential dissectinginstrument of claim 18, wherein the difference between the minimumplacement radius, R_(min), and the maximum placement radius, R_(max), isequal to or greater than an average length, P_(avg), of the projections,i.e. (R_(max)−R_(min))≧P_(avg).
 21. The differential dissectinginstrument of claim 18, wherein R_(max) is greater than one (1) mm butless than one hundred (100) mm.
 22. The differential dissectinginstrument of claim 18, wherein R_(max) is greater than 0.5 mm but lessthan five (5) mm.
 23. A differential dissecting member for dissecting acomplex tissue, the differential dissecting member comprising: a bodyhaving a first end and a second end with a central axis from the firstend to the second end; wherein the first end is configured to bedirected away from the complex tissue and configured to be engaged witha drive mechanism that moves the differential dissecting member suchthat the second end sweeps along a direction of motion, and wherein thesecond end comprises a tissue-facing surface that is configured to bedirected toward the complex tissue; wherein the tissue-facing surfacecomprises at least one tissue engaging surface comprised of analternating series of at least one valley and at least one projectionarrayed along the direction of motion on the tissue-facing surface suchthat the intersection of the at least one valley and at least oneprojection define at least one valley edge's possessing a component ofthe at least one valley edge's direction perpendicular to the directionof motion, and wherein the tissue-facing surface comprises asemi-ellipsoid shape defined by three orthogonal semi-axes, the threeorthogonal semi-axes comprising a major semi-axis A, a first minorsemi-axis B, and a second minor semi-axis C, and wherein the majorsemi-axis A is perpendicular to the axis of rotation, the secondsemi-minor axis C is parallel to the axis of rotation, and the firstminor semi-axis B is perpendicular to both the major semi-axis A and thesecond semi-minor axis C.
 24. The differential dissecting member ofclaim 23, wherein the at least one valley edge is not sharp.
 25. Thedifferential dissecting member of claim 23, wherein the differentialdissecting member is configured to rotate around an axis of rotationoriented perpendicular to the central axis of the differentialdissecting member such that the direction of motion of the second end isan arc of motion.
 26. The differential dissecting member of claim 25,wherein the rotation is a reciprocal (back-and-forth) oscillation. 27.The differential dissecting member of claim 25, wherein the rotation isbetween sixty (60) and twenty-five thousand (25,000) cycles per minute.28. The differential dissecting member of claim 25, wherein the rotationis between sixty (60) and one million (1,000,000) cycles per minute. 29.The differential dissecting member of claim 23, wherein the at least onevalley edge has a radius of curvature at no point being smaller than0.025 mm.
 30. The differential dissecting member of claim 23, whereinthe at least one valley edge has a radius of curvature at no point beingsmaller than 0.05 mm.
 31. The differential dissecting member of claim23, wherein the at least one valley edge has a radius of curvature thatvaries along a length of the at least one valley edge.
 32. Thedifferential dissecting member of claim 31, wherein the radius ofcurvature of the at least one valley edge is smallest at points furthestfrom the axis of rotation.
 33. The differential dissecting member ofclaim 23, wherein the at least one projection further comprises aprojection top formed by the tissue-facing surface spanning from a firstvalley edge on one side of the projection to a second valley edge on theopposing side of the projection.
 34. The differential dissecting memberof claim 23, wherein the at least one valley further comprises a valleybottom, a first valley wall abutting one side of the valley bottom, anda second valley wall abutting the opposing side of the valley bottomsuch that each valley wall joins a projection top at at least one valleyedge.
 35. The differential dissecting member of claim 34, wherein thefirst and second valley walls are straight in the direction parallel tothe axis of rotation.
 36. The differential dissecting member of claim34, wherein at least one of the first and second valley walls is curvedin three dimensions.
 37. The differential dissecting member of claim 34,wherein at least one of the first and second valley walls and theprojection top form a face angle ┌ that is less than ninety degrees(90°).
 38. The differential dissecting member of claim 34, wherein atleast one of the first and second valley walls and the projection topform a face angle ┌ that ranges from thirty degrees (30°) to one hundredfifty degrees (150°).
 39. The differential dissecting member of claim23, wherein the at least one valley edge traces a three-dimensionalcurve.
 40. The differential dissecting member of claim 39, wherein thethree-dimensional curve varies along a length of the three-dimensionalcurve.
 41. The differential dissecting member of claim 23, wherein theat least one valley has a maximum depth of between 0.1 mm to five (5)mm.
 42. The differential dissecting member of claim 23, wherein the atleast one valley has a maximum width of between 0.1 mm to five (5) mm.43. The differential dissecting member of claim 23, wherein the at leastone valley has a minimum length of 0.25 mm.
 44. The differentialdissecting member of claim 23, wherein the at least one valley comprisestwo or more valleys.
 45. The differential dissecting member of claim 44,wherein the two or more valleys are approximately parallel to eachother.
 46. The differential dissecting member of claim 23, the at leastone valley is comprised of multiple, intersecting valleys.
 47. Thedifferential dissecting member of claim 23, wherein the major semi-axisA, the first minor semi-axis B, and the second minor semi-axis C allhave different lengths (A≠B≠C).
 48. The differential dissecting memberof claim 23, wherein the major semi-axis A is longer than the firstminor semi-axis B and the second minor semi-axis C (A>B and A>C). 49.The differential dissecting member of claim 23, wherein the majorsemi-axis A is longer than first minor semi-axis B, which is longer thanthe second minor semi-axis C (A>B>C), and the second minor semi-axis Cis parallel to the direction of motion.
 50. The differential dissectingmember of claim 23, wherein the differential dissecting member furthercomprises at least one lateral surface disposed beside the tissueengaging surface.
 51. The differential dissecting member of claim 50,wherein the at least one lateral surface is configured to exert awedging force on the complex tissue when the differential dissectingmember is pressed into the complex tissue.
 52. The differentialdissecting member of claim 50, wherein the at least one lateral surfacecomprises a first lateral surface disposed on one side of the tissueengaging surface and a second lateral surface disposed on the opposingside of the tissue engaging surface, and wherein the first and secondlateral surfaces are configured to exert a wedging force on the complextissue when the differential dissecting member is pressed into thecomplex tissue.
 53. The differential dissecting member of claim 52,wherein at least one valley spans from the first lateral surface to thesecond lateral surface and thus crosses an entirety of the tissueengaging surface.
 54. The differential dissecting member of claim 23,wherein an entirety of the tissue contacting surface of the differentialdissecting member is smooth and composed entirely of a material having alow friction with respect to the complex tissue.
 55. The differentialdissecting member of claim 23, wherein the tissue facing surface islubricated.
 56. The differential dissecting instrument of claim 1,wherein the major semi-axis A is longer than first minor semi-axis B,which is longer than the second minor semi-axis C (A>B>C), and thesecond minor semi-axis C is parallel to the axis of rotation.
 57. Adifferential dissecting instrument for differentially dissecting complextissue comprising: a handle; an elongate member having a first end and asecond end, the first end connected to the handle; a differentialdissecting member configured to be rotatably attached to the second end,the differential dissecting member comprising at least one tissueengaging surface; and a mechanism configured to mechanically rotate thedifferential dissecting member around an axis of rotation therebycausing the at least one tissue engaging surface to move in at least onedirection against the complex tissue, wherein the at least one tissueengaging surface is configured to selectively engage the complex tissuesuch that when the differential dissecting member is pressed into thecomplex tissue, the at least one tissue engaging surface moves acrossthe complex tissue and the at least one tissue engaging surface disruptsat least one soft tissue in the complex tissue, but does not disruptfirm tissue in the complex tissue, wherein the differential dissectingmember comprises a body; and further comprises a tissue engaging surfacedistributed over at least a portion of the outer surface of the body andhaving: a minimum placement radius, R_(min), along a line perpendicularto the axis of rotation measured from the axis of rotation to a point onthe tissue engaging surface closest to the axis of rotation, a maximumplacement radius, R_(max), along a line perpendicular to the axis ofrotation measured from the axis of rotation to a point on the tissueengaging surface furthest from the axis of rotation, and the minimumplacement radius, R_(min), is greater than zero; and wherein thedifference between the minimum placement radius, R_(min), and themaximum placement radius, R_(max), is equal to or greater than 5% ofR_(max), i.e. (R_(max)−R_(min))≧0.05*R_(max).
 58. A differentialdissecting instrument for differentially dissecting complex tissuecomprising: a handle; an elongate member having a first end and a secondend, the first end connected to the handle; a differential dissectingmember configured to be rotatably attached to the second end, thedifferential dissecting member comprising at least one tissue engagingsurface; and a mechanism configured to mechanically rotate thedifferential dissecting member around an axis of rotation therebycausing the at least one tissue engaging surface to move in at least onedirection against the complex tissue, wherein the at least one tissueengaging surface is configured to selectively engage the complex tissuesuch that when the differential dissecting member is pressed into thecomplex tissue, the at least one tissue engaging surface moves acrossthe complex tissue and the at least one tissue engaging surface disruptsat least one soft tissue in the complex tissue, but does not disruptfirm tissue in the complex tissue, wherein the differential dissectingmember comprises a body; and further comprises a tissue engaging surfacedistributed over at least a portion of the outer surface of the body andhaving: a minimum placement radius, R_(min), along a line perpendicularto the axis of rotation measured from the axis of rotation to a point onthe tissue engaging surface closest to the axis of rotation, a maximumplacement radius, R_(max), along a line perpendicular to the axis ofrotation measured from the axis of rotation to a point on the tissueengaging surface furthest from the axis of rotation, and the minimumplacement radius, R_(min), is greater than zero; and wherein thedifference between the minimum placement radius, R_(min), and themaximum placement radius, R_(max), is equal to or greater than anaverage length, P_(avg), of the projections, i.e.(R_(max)−R_(min))≧P_(avg).